The following code draws only a green box, when I am expecting both a green and red box.
If I don't have the second glClear() statement, the red box appears.
This leads me to conclude, since I have the scissor box outside the bounds of the red box, that the glClear() statement is not respecting the scissor box.
Can anyone help me understand what is going on?
glEnable(GL_SCISSOR_TEST);
int x, y, w, h;
x = 0;
y = 0;
w = 700;
h = 700;
glViewport(x,y,w,h);
glScissor(x,y,w,h);
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
x = 0;
y = 750;
w = 700;
h = 700;
glViewport(x,y,w,h);
glScissor(x,y,w,h);
glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
So I managed to figure this out myself. I had to "reset" the scissor box at the end of the draw call. i.e.:
glScissor(0,0,viewPixelWidth, viewPixelHeight);
What was happening was that when the renderbuffer was being presented, the scissor box was being applied again, therefore everything outside the latest scissor box was not copied.
Related
Sorry for auto translation.
The part that's stuck right now is shadow mapping.
The position of the player is exactly 2000, 0, 2000; there is a light source that is the origin of the shadow mapping camera directly over the sky (it is a directory light).
Question 1
You need a shadow map to apply shadow mapping, don't you?
The shadow map isn't working right now, but let's move on.
As long as the viewport of the shadow mapping camera is in the cover space itself, the render is not working properly on the shadow map.
Even if it's initialized to 1.0f, it's all supposed to be outside the shadows.
Although the current shadow map camera position is 2000, 100, 2000, and the focus position is 0, 0, 0.
It's not a red square area that's supposed to be determined to be outside the shadow.
The green square area is determined to be out of the shadow.
For your information, there's nothing blocking the light in the viewport. The shadow you see in the screenshot is just outside the viewport, so it's a shadow that comes from a 0.0f judgment on the shadow map.
Question 2
This is the fundamental problem. No render on shadow map in shadow pass.
Once this is done, I'll find the first question somehow, but the render itself doesn't work, so there's no shadow of the object -> the cause is unknown
Source indicates that the ShadowShader class is rendering a shadow map (ShadowPassRender)
What affects this is the degree of view-project matrix created at the time of the light source (the Update ShaderVariables portion of the Shadow Shader class).
I'm most suspicious of this one, but the process of making it is not different from the example, so I don't know where it's wrong.
I'm using the light itself as a blin pong, and I'm gonna take this as an example and fix it for the project.
code that generate View-Projection matrix for shadow mapping
void CShadowShader::UpdateShaderVariables(ID3D12GraphicsCommandList* pd3dCommandList, XMFLOAT3 xmf3TargetPos)
{
XMFLOAT3 TargetPos = {950, 0, 950};
XMMATRIX lightView = XMMatrixLookAtLH(XMLoadFloat3(&m_pLight->GetPosition()), XMLoadFloat3(&TargetPos), XMLoadFloat3(&m_pLight->GetUp()));
// Transform bounding sphere to light space.
XMFLOAT3 xmf3CenterLS;
XMStoreFloat3(&xmf3CenterLS, XMVector3TransformCoord(XMLoadFloat3(&TargetPos), lightView));
// Ortho frustum in light space encloses scene.
float l = xmf3CenterLS.x - 3000;
float b = xmf3CenterLS.y - 3000;
float n = xmf3CenterLS.z - 3000;
float r = xmf3CenterLS.x + 3000;
float t = xmf3CenterLS.y + 3000;
float f = xmf3CenterLS.z + 3000;
XMMATRIX lightProj = XMMatrixOrthographicOffCenterLH(l, r, b, t, n, f);
// Transform NDC space [-1,+1]^2 to texture space [0,1]^2
XMMATRIX T(
0.5f, 0.0f, 0.0f, 0.0f,
0.0f, -0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.0f, 1.0f);
XMMATRIX S = lightView * lightProj * T;
XMFLOAT4X4 m_xmf4x4ShadowTransform;
XMStoreFloat4x4(&m_xmf4x4ShadowTransform, S);
CB_SHADOW cbShadow{ m_xmf4x4ShadowTransform, m_pLight->GetPosition() };
m_ubShadowCB->CopyData(0, cbShadow);
pd3dCommandList->SetGraphicsRootConstantBufferView(3, m_ubShadowCB->Resource()->GetGPUVirtualAddress());
}
make PSO for shadow pass
void CShadowShader::CreateShader(ID3D12Device* pd3dDevice, ID3D12RootSignature* pd3dGraphicsRootSignature)
{
m_ubShadowCB = new UploadBuffer<CB_SHADOW>(pd3dDevice, 1, true);
ID3DBlob* pd3dVertexShaderBlob = NULL, * pd3dPixelShaderBlob = NULL;
D3D12_GRAPHICS_PIPELINE_STATE_DESC d3dPipelineStateDesc;
::ZeroMemory(&d3dPipelineStateDesc, sizeof(D3D12_GRAPHICS_PIPELINE_STATE_DESC));
d3dPipelineStateDesc.pRootSignature = pd3dGraphicsRootSignature;
d3dPipelineStateDesc.VS = CreateVertexShader(&pd3dVertexShaderBlob);
d3dPipelineStateDesc.PS = CreatePixelShader(&pd3dPixelShaderBlob);
d3dPipelineStateDesc.RasterizerState = CreateRasterizerState();
d3dPipelineStateDesc.RasterizerState.DepthBias = 10000.0f;
d3dPipelineStateDesc.RasterizerState.DepthBiasClamp = 0.0f;
d3dPipelineStateDesc.RasterizerState.SlopeScaledDepthBias = 1.0f;
d3dPipelineStateDesc.BlendState = CreateBlendState();
d3dPipelineStateDesc.DepthStencilState = CreateDepthStencilState();
d3dPipelineStateDesc.InputLayout = CreateInputLayout();
d3dPipelineStateDesc.SampleMask = UINT_MAX;
d3dPipelineStateDesc.PrimitiveTopologyType = D3D12_PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE;
d3dPipelineStateDesc.NumRenderTargets = 0;
d3dPipelineStateDesc.RTVFormats[0] = DXGI_FORMAT_UNKNOWN;
d3dPipelineStateDesc.DSVFormat = DXGI_FORMAT_D24_UNORM_S8_UINT;
d3dPipelineStateDesc.SampleDesc.Count = 1;
d3dPipelineStateDesc.Flags = D3D12_PIPELINE_STATE_FLAG_NONE;
auto tmp = pd3dDevice->CreateGraphicsPipelineState(&d3dPipelineStateDesc, __uuidof(ID3D12PipelineState), (void**)&m_pd3dPipelineState);
if (pd3dVertexShaderBlob)
pd3dVertexShaderBlob->Release();
if (pd3dPixelShaderBlob)
pd3dPixelShaderBlob->Release();
if (d3dPipelineStateDesc.InputLayout.pInputElementDescs)
delete[] d3dPipelineStateDesc.InputLayout.pInputElementDescs;
}
Shader for Shadow pass
#include "Common.hlsli"
struct VertexIn
{
float3 PosL : POSITION;
};
struct VertexOut
{
float4 PosH : SV_POSITION;
};
VertexOut VS(VertexIn vin)
{
VertexOut vout = (VertexOut) 0.0f;
MATERIAL matData = material;
// Transform to world space.
float4 posW = mul(float4(vin.PosL, 1.0f), gmtxWorld);
// Transform to homogeneous clip space.
vout.PosH = mul(posW, gmtxShadowTransform);
return vout;
}
// This is only used for alpha cut out geometry, so that shadows
// show up correctly. Geometry that does not need to sample a
// texture can use a NULL pixel shader for depth pass.
void PS(VertexOut pin)
{
// Fetch the material data.
MATERIAL matData = material;
float4 diffuseAlbedo = matData.DiffuseAlbedo;
}
Default.hlsl for render pass (there's few korean comments. not important)
#include "Common.hlsli"
//정점 셰이더의 입력을 위한 구조체를 선언한다.
struct VS_DEFAULT_INPUT
{
float3 position : POSITION;
float3 normal : NORMAL;
};
//정점 셰이더의 출력(픽셀 셰이더의 입력)을 위한 구조체를 선언한다.
struct VS_DEFAULT_OUTPUT
{
float4 position : SV_POSITION;
float4 position_shadow : POSITION0;
float3 position_w : POSITION1;
float3 normal : NORMAL;
};
VS_DEFAULT_OUTPUT VS_Default(VS_DEFAULT_INPUT input)
{
VS_DEFAULT_OUTPUT output;
output.position = mul(mul(float4(input.position, 1.0f), gmtxWorld), gmtxViewProj);
output.position_w = mul(float4(input.position, 1.0f), gmtxWorld).xyz;
output.normal = normalize(mul(float4(input.normal, 0.0f), gmtxWorld).xyz);
output.position_shadow = mul(float4(output.position_w, 1.0f), gmtxShadowTransform);
return (output);
}
float4 PS_Default(VS_DEFAULT_OUTPUT input) : SV_TARGET
{
float4 cColor = float4(0.0f, 0.0f, 0.0f, 0.0f);
cColor += material.AmbientLight * material.DiffuseAlbedo;
float3 toEyeW = normalize(cameraPos - input.position_w);
float3 shadowFactor = float3(1.0f, 1.0f, 1.0f);
shadowFactor[0] = CalcShadowFactor(input.position_shadow);
for (int i = 0; i < nLights; i++)
{
cColor += ComputeLighting(light[i], input.position_w, input.normal, toEyeW, shadowFactor[0]);
}
// Add in specular reflections.
float3 r = reflect(-toEyeW, input.normal);
float4 reflectionColor = { 1.0f, 1.0f, 1.0f, 0.0f };
float3 fresnelFactor = SchlickFresnel(material.FresnelR0, input.normal, r);
cColor.rgb += material.Shininess * fresnelFactor * reflectionColor.rgb;
// Common convention to take alpha from diffuse albedo.
cColor.a = material.DiffuseAlbedo.a;
return (cColor);
}
GitHub Link: https://github.com/kcjsend2/3DGP-BulletPhysics
Bullet physical engine is included, so bullet engine will need to be received and connected to the project to build.
See Chapter 20 Shadow Mapping in Frank Luna's Introduction to 3d game programming with directx 12 for examples.
The framework is independent, so it's very different from the example.
Bullet physics engine is included, so bullet engine will need to be received and connected to the project to build.
I fixed it. just because of hlsl shader and direct x uses different type of matrix.
hlsl shader uses column major, and direct x uses row major matrix.
and I also calculate wrong with matrix multipication order.
worng one is first codes of the question
...and this is fixed code:
XMVECTOR lightPos = XMLoadFloat3(&m_pLight->GetPosition());
XMVECTOR TargetPos = XMLoadFloat3(&xmf3TargetPos);
XMVECTOR lightUp = XMLoadFloat3(&m_pLight->GetUp());
XMMATRIX lightView = XMMatrixLookAtLH(lightPos, TargetPos, lightUp);
/*XMVECTOR lightLook = Vector3::Normalize(lightPos - TargetPos);*/
// Transform bounding sphere to light space.
XMFLOAT3 xmf3CenterLS;
XMStoreFloat3(&xmf3CenterLS, XMVector3TransformCoord(XMLoadFloat3(&xmf3TargetPos), lightView));
// Ortho frustum in light space encloses scene.
float l = xmf3CenterLS.x - 800;
float b = xmf3CenterLS.y - 800;
float n = xmf3CenterLS.z - 800;
float r = xmf3CenterLS.x + 800;
float t = xmf3CenterLS.y + 800;
float f = xmf3CenterLS.z + 800;
XMMATRIX lightProj = XMMatrixOrthographicOffCenterLH(l, r, b, t, n, f);
// Transform NDC space [-1,+1]^2 to texture space [0,1]^2
XMMATRIX T(
0.5f, 0.0f, 0.0f, 0.0f,
0.0f, -0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.0f, 1.0f);
XMMATRIX S = lightView * lightProj;
XMFLOAT4X4 xmf4x4LightViewProj;
XMStoreFloat4x4(&xmf4x4LightViewProj, XMMatrixTranspose(S));
S = S * T;
XMFLOAT4X4 xmf4x4ShadowTransform;
XMStoreFloat4x4(&xmf4x4ShadowTransform, XMMatrixTranspose(S));
CB_SHADOW cbShadow{ xmf4x4ShadowTransform, xmf4x4LightViewProj, m_pLight->GetPosition() };
m_ubShadowCB->CopyData(0, cbShadow);
pd3dCommandList->SetGraphicsRootConstantBufferView(3, m_ubShadowCB->Resource()->GetGPUVirtualAddress());
Exactly the same issue I was facing when I was not transposing the matrix I was sending to shader, then I transposed it and it worked. :)
By now points can be drawn with the following code:
// SETUP FOR VERTICES
GLfloat points[graph->vertexCount * 6];
for (int i = 0 ; i < graph->vertexCount; i++)
{
points[i*6] = (graph->vertices[i].x / (backingWidth/2) ) - 1;
points[i*6+1] = -(graph->vertices[i].y / (backingHeight/2) ) + 1;
points[i*6+2] = 1.0;
points[i*6+3] = 0.0;
points[i*6+4] = 0.0;
points[i*6+5] = 1.0;
}
glEnable(GL_POINT_SMOOTH);
glPointSize(DOT_SIZE*scale);
glVertexPointer(2, GL_FLOAT, 24, points);
glColorPointer(4, GL_FLOAT, 24, &points[2]);
glDrawArrays(GL_POINTS, 0, graph->vertexCount);
The points are rendered with red color, and I want to add a white outline outside the points. How can I draw outline of the point?
Question for better displaying
Follow #BDL 's instruction adding bigger points under the red points as outline, they look good.
outlinePoints[i*6] = (graph->vertices[i].x / (backingWidth/2) ) - 1;
outlinePoints[i*6+1] = -(graph->vertices[i].y / (backingHeight/2) ) + 1;
outlinePoints[i*6+2] = 0.9;
outlinePoints[i*6+3] = 0.9;
outlinePoints[i*6+4] = 0.9;
outlinePoints[i*6+5] = 1.0;
But when one point overlaps another point, it's outline is covered by the red point, since the outline points are rendered before all the red points.
I think the right solution is to render one outline point and red point one by one. How to do that?
If you want to render outlines for each point separately, then you can simply render a slightly larger white point first and then render the red point over it. With depth-testing enabled, you might have to adjust the polygon offset when rendering the red point to prevent them from getting hidden behind the white ones.
I want to draw object within ar but got unexpected result - gl mashine think that i see object from another side (or from inside).
Here image what i want to draw (taken from separate project)
And here - what i got when try to draw this object in my ar (inside of the sphere)
So I guess that problem is that because I put object inside sphere and adjust position of obj using base mat from sphere obj.
Camera positioned in the center of the sphere - so for this obj I use same mat - just scale/rotate/translate it.
This is how I calculate projection mat
CGRect viewFrame = self.frame;
if (!CGSizeEqualToSize(self.newSize, CGSizeZero){
size = self.newSize;
}
CGFloat aspect = viewFrame.size.width / viewFrame.size.height;
CGFloat scale = self.interractor.scale;
CGFloat FOVY = DEGREES_TO_RADIANS(self.viewScale) / scale;
CGFloat cameraDistanse = -(1.0 / [Utilities FarZ]);
GLKMatrix4 cameraTranslation = GLKMatrix4MakeTranslation(0, 0, cameraDistanse);
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(FOVY, aspect, NearZ, [Utilities FarZ]);
projectionMatrix = GLKMatrix4Multiply(projectionMatrix, cameraTranslation);
//and also here added some code for modifying, but I skip it here
For this obj I just calculate new scale and position of obj - looks like it's correct because I able to see obj and change his position etc, so skip this part.
In the second project where I got correct result of displaying obj I calculate projection mat in similar way, but with a little bit less calculation:
float aspect = self.glView.frame.size.width / self.glView.frame.size.height;
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.01f, 100);
//scale
//rotate
//translate
GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.5f);
modelViewMatrix = GLKMatrix4Multiply(modelViewMatrix, projectionMatrix);
GLfloat scale = 0.5 *_scale;
GLKMatrix4 scaleMatrix = GLKMatrix4MakeScale(scale, scale, scale);
modelViewMatrix = GLKMatrix4Translate(modelViewMatrix, _positionX, _positionY, -5);
modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotationX, 0.0f, 1.0f, 0.0f);
modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotationY, 1.0f, 0.0f, 0.0f);
modelViewMatrix = GLKMatrix4Multiply(scaleMatrix, modelViewMatrix);
In first project (correct one) I also use
glEnable(GL_DEPTH_TEST);
glDepthMask(GL_TRUE);
glDisable(GL_CULL_FACE);
In second with few obj - depend from obj that I want to draw:
glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDisable(GL_SCISSOR_TEST);
glDisable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);
//call sphere draw
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
//call obj draw
glEnable(GL_SCISSOR_TEST);
So as I sad before, I guess that the problem is that openGL "think" that we are looking to obj from another side, but I'm not sure. And if i'm right how can i fix this? Or whats done incorrect?
Update
#codetiger I check ur suggestions:
1) Wrong face winding order - recheck it again and try to inverse order, also try to build same model in another project (all works perfect) - result i guess that order is ok;
2) Wrong Culling - check all combinations of
glDisable / glEnable with argument GL_CULL_FACE
glCullFace with argument GL_FRONT, GL_BACK or GL_FRONT_AND_BACK
glFrontFace with argument GL_CW or GL_CCW
What i see - a little bit change but i see still incorrect obj (or wrong side or partial obj etc)
3) vertices are flipped - try to flip them, as result - even worse than before
4) try to combine this 3 suggestion one with another - result not acceptable
I have a very simple VS and PS that are supposed to draw a screen-sized quad on the screen. However, my tests to colorize based on texture coordinate are showing a solid color across the entire rect (screen) instead of interpolated fading colors along the x and y direction. Here is my shader code:
struct FRAGMENT {float4 position:SV_POSITION; float3 tex_coord:TEXCOORD0;};
FRAGMENT vs_main(uint vertex_id : SV_VertexID) {
FRAGMENT OUT;
OUT.tex_coord = float3(0.0f,0.0f,0.0f);
if(vertex_id == 1) OUT.tex_coord.x = 1.0f;
else if(vertex_id == 2) OUT.tex_coord.y = 1.0f;
else if(vertex_id == 3) OUT.tex_coord.xy = float2(1.0f, 1.0f);
OUT.position = float4(OUT.tex_coord.x * 2.0f - 1.0f, OUT.tex_coord.y * 2.0f - 1.0f, 0.0f, 0.0f);
return OUT;
}
float4 ps_main(FRAGMENT IN) : SV_TARGET {
return float4(IN.tex_coord, 1.0f);
}
The quad draws just fine, and I can color it manually, but the value for IN.tex_coord is solid across the entire screen. Does anyone know what is wrong?
About 2 days ago I decided to write code to explicitly calculate the Model-View-Projection ("MVP") matrix to understand how it worked. Since then I've had nothing but trouble, seemingly because of the projection matrix I'm using.
Working with an iPhone display, I create a screen centered square described by these 4 corner vertices:
const CGFloat cy = screenHeight/2.0f;
const CGFloat z = -1.0f;
const CGFloat dim = 50.0f;
vxData[0] = cx-dim;
vxData[1] = cy-dim;
vxData[2] = z;
vxData[3] = cx-dim;
vxData[4] = cy+dim;
vxData[5] = z;
vxData[6] = cx+dim;
vxData[7] = cy+dim;
vxData[8] = z;
vxData[9] = cx+dim;
vxData[10] = cy-dim;
vxData[11] = z;
Since I am using OGLES 2.0 I pass the MVP as a uniform to my vertex shader, then simply apply the transformation to the current vertex position:
uniform mat4 mvp;
attribute vec3 vpos;
void main()
{
gl_Position = mvp * vec4(vpos, 1.0);
}
For now I have simplified my MVP to just be the P matrix. There are two projection matrices listed in the code shown below. The first is the standard perspective projection matrix, and the second is an explicit-value projection matrix I found online.
CGRect screenBounds = [[UIScreen mainScreen] bounds];
const CGFloat screenWidth = screenBounds.size.width;
const CGFloat screenHeight = screenBounds.size.height;
const GLfloat n = 0.01f;
const GLfloat f = 100.0f;
const GLfloat fov = 60.0f * 2.0f * M_PI / 360.0f;
const GLfloat a = screenWidth/screenHeight;
const GLfloat d = 1.0f / tanf(fov/2.0f);
// Standard perspective projection.
GLKMatrix4 projectionMx = GLKMatrix4Make(d/a, 0.0f, 0.0f, 0.0f,
0.0f, d, 0.0f, 0.0f,
0.0f, 0.0f, (n+f)/(n-f), -1.0f,
0.0f, 0.0f, (2*n*f)/(n-f), 0.0f);
// The one I found online.
GLKMatrix4 projectionMx = GLKMatrix4Make(2.0f/screenWidth,0.0f,0.0f,0.0f,
0.0f,2.0f/-screenHeight,0.0f,0.0f,
0.0f,0.0f,1.0f,0.0f,
-1.0f,1.0f,0.0f,1.0f);
When using the explicit value matrix, the square renders exactly as desired in the centre of the screen with correct dimension. When using the perspective projection matrix, nothing is displayed on-screen. I've done printouts of the position values generated for screen centre (screenWidth/2, screenHeight/2, 0) by the perspective projection matrix and they're enormous. The explicit value matrix correctly produces zero.
I think the explicit value matrix is an orthographic projection matrix - is that right? My frustration is that I can't work out why my perspective projection matrix fails to work.
I'd be tremendously grateful if someone could help me with this problem. Many thanks.
UPDATE For Christian Rau:
#define Zn 0.0f
#define Zf 100.0f
#define PRIMITIVE_Z 1.0f
//...
CGRect screenBounds = [[UIScreen mainScreen] bounds];
const CGFloat screenWidth = screenBounds.size.width;
const CGFloat screenHeight = screenBounds.size.height;
//...
glUseProgram(program);
//...
glViewport(0.0f, 0.0f, screenBounds.size.width, screenBounds.size.height);
//...
const CGFloat cx = screenWidth/2.0f;
const CGFloat cy = screenHeight/2.0f;
const CGFloat z = PRIMITIVE_Z;
const CGFloat dim = 50.0f;
vxData[0] = cx-dim;
vxData[1] = cy-dim;
vxData[2] = z;
vxData[3] = cx-dim;
vxData[4] = cy+dim;
vxData[5] = z;
vxData[6] = cx+dim;
vxData[7] = cy+dim;
vxData[8] = z;
vxData[9] = cx+dim;
vxData[10] = cy-dim;
vxData[11] = z;
//...
const GLfloat n = Zn;
const GLfloat f = Zf;
const GLfloat fov = 60.0f * 2.0f * M_PI / 360.0f;
const GLfloat a = screenWidth/screenHeight;
const GLfloat d = 1.0f / tanf(fov/2.0f);
GLKMatrix4 projectionMx = GLKMatrix4Make(d/a, 0.0f, 0.0f, 0.0f,
0.0f, d, 0.0f, 0.0f,
0.0f, 0.0f, (n+f)/(n-f), -1.0f,
0.0f, 0.0f, (2*n*f)/(n-f), 0.0f);
//...
// ** Here is the matrix you recommended, Christian:
GLKMatrix4 ts = GLKMatrix4Make(2.0f/screenWidth, 0.0f, 0.0f, -1.0f,
0.0f, 2.0f/screenHeight, 0.0f, -1.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f);
GLKMatrix4 mvp = GLKMatrix4Multiply(projectionMx, ts);
UPDATE 2
The new MVP code:
GLKMatrix4 ts = GLKMatrix4Make(2.0f/screenWidth, 0.0f, 0.0f, -1.0f,
0.0f, 2.0f/-screenHeight, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f);
// Using Apple perspective, view matrix generators
// (I can solve bugs in my own implementation later..!)
GLKMatrix4 _p = GLKMatrix4MakePerspective(60.0f * 2.0f * M_PI / 360.0f,
screenWidth / screenHeight,
Zn, Zf);
GLKMatrix4 _mv = GLKMatrix4MakeLookAt(0.0f, 0.0f, 1.0f,
0.0f, 0.0f, -1.0f,
0.0f, 1.0f, 0.0f);
GLKMatrix4 _mvp = GLKMatrix4Multiply(_p, _mv);
GLKMatrix4 mvp = GLKMatrix4Multiply(_mvp, ts);
Still nothing visible at the screen centre, and the transformed x,y coordinates of the screen centre are not zero.
UPDATE 3
Using the transpose of ts instead in the above code works! But the square no longer appears square; it appears to now have aspect ratio screenHeight/screenWidth i.e. it has a longer dimension parallel to the (short) screen width, and a shorter dimension parallel to the (long) screen height.
I'd very much like to know (a) why the transpose is required and whether it is a valid fix, (b) how to correctly rectify the non-square dimension, and (c) how this additional matrix transpose(ts) that we use fits into the transformation chain of Viewport * Projection * View * Model * Point .
For (c): I understand what the matrix does, i.e. the explanation by Christian Rau as to how we transform to range [-1, 1]. But is it correct to include this additional work as a separate transformation matrix, or should some part of our MVP chain be doing this work instead?
Sincere thanks go to Christian Rau for his valuable contribution thus far.
UPDATE 4
My question about "how ts fits in" is silly isn't it - the whole point is the matrix is only needed because I'm choosing to use screen coordinates for my vertices; if I were to use coordinates in world space from the start then this work wouldn't be needed!
Thanks Christian for all your help, it's been invaluable :) Problem solved.
The reason for this is, that your first projection matrix doesn't account for the scaling and translation part of the transformation, whereas the second matrix does it.
So, since your modelview matrix is identity, the first projection matrix assumes the models' coordinates to ly somewhere in [-1,1], whereas the second matrix already contains the scaling and translation part (look at the screenWidth/Height values in there) and therefore assumes the coordinates to ly in [0,screenWidth] x [0,screenHeight].
So you have to right-multiply your projection matrix by a matrix that first scales [0,screenWidth] down to [0,2] and [0,screenHeight] down to [0,2] and then translates [0,2] into [-1,1] (using w for screenWidth and h for screenHeight):
[ 2/w 0 0 -1 ]
[ 0 2/h 0 -1 ]
[ 0 0 1 0 ]
[ 0 0 0 1 ]
which will result in the matrix
[ 2*d/h 0 0 -d/a ]
[ 0 2*d/h 0 -d ]
[ 0 0 (n+f)/(n-f) 2*n*f/(n-f) ]
[ 0 0 -1 0 ]
So you see that your second matrix corresponds to a fov of 90 degrees, an aspect ratio of 1:1 and a near-far range of [-1,1]. Additionally it also inverts the y-axis, so that the origin is in the upper-left, which results in the second row being negated:
[ 0 -2*d/h 0 d ]
But as an end comment, I suggest you to not configure the projection matrix to account for all this. Instead your projection matrix should look like the first one and you should let the modelview matrix manage any translation or scaling of your world. It is not by accident, that the transformation pipeline was seperated into modelview and projection matrix and you should keep this separation also when using shaders. You can of course still multiply both matrices together on the CPU and upload a single MVP matrix to the shader.
And in general you don't really use a screen-based coordinate system when working with a 3-dimensional world. You would only want to do this if you are drawing 2d graphics (like GUI elements or HUDs) and in this case you would use a more simple orthographic projection matrix, anyway, that is nothing more than the above mentioned scale-translate matrix without all the perspective complexity.
EDIT: To your 3rd update:
(a) The transpose is required because I guess your GLKMatrix4Make function accepts its parameters in column-major format and you put the matrix in row-wise.
(b) I made a little mistake. You should change the screenWidth in the ts matrix into screenHeight (or maybe the other way around, not sure). We actually need a uniform scale, because the aspect ratio is already taken care of by the projection matrix.
(c) It is not easy to classify this matrix into the usual MVP pipeline. This is because it is not really common. Let's look at the two common cases of rendering:
3D: When you have a 3-dimensional world it is not really common to define it's coordinates in screen-based units, because there is not et a mapping from 3d-scene to 2d-screen and using a coordinate system where units equal pixels just doesn't make sense. In this setup you most likely would classify it as part of the modelview matrix for transforming the world into another unit system. But in this case you would need real 3d transformations and not just such a half-baked 2d solution.
2D: When rendering a 2d-scene (like a GUI or a HUD or just some text), you sometimes really want a screen-based coordinate system. But in this case you most likely would use an orthographic projection (without any perspective). Such an orthographic matrix is actually nothing more than this ts matrix (with some additional scale-translate for z, based on the near-far range). So in this case the matrix belongs to, or actually is, the projection matrix. Just look at how the good old glOrtho function constructs its matrix and you'll see its nothing more than ts.