I'm in the process of writing my first few shaders, usually writing a shader to accomplish features as I realize that the main XNA library doesn't support them.
The trouble I'm running into is that not all of my models in a particular scene have texture data in them, and I can't figure out how to handle that. The main XNA libraries seem to handle it by using a wrapper class for BasicEffect, loading it through the content manager and selectively enabling or disabling texture processing accordingly.
How difficult is it to accomplish this for a custom shader? What I'm writing is an generic "hue shift" effect, that is, I want whatever gets drawn with this technique to have its texture colors (if any) and its vertex color hue shifted by a certain degree. Do I need to write separate shaders, one with textures and one without? If so, when I'm looping through my MeshParts, is there any way to detect if a given part has texture coordinates so that I can apply the correct effect?
Yes, you will need separate shaders, or rather different "techniques" - it can still be the same effect and use much of the same code. You can see how BasicEffect (at least the pre-XNA 4.0 version) does it by reading the source code.
To detect whether or not a model mesh part has texture coordinates, try this:
// Note: this allocates an array, so do it at load-time
var elements = meshPart.VertexBuffer.VertexDeclaration.GetVertexElements();
bool result = elements.Any(e =>
e.VertexElementUsage == VertexElementUsage.TextureCoordinate);
The way the content pipeline sets up its BasicEffect is via BasicMaterialContent. The BasicEffect.TextureEnabled property is simply turned on if Texture is set.
Related
I have a simple program that renders a couple of 3D objects, using DirectX 3D 9 and HLSL. I'm just starting off with HLSL, I have no experience with 3D rendering.
I am able to change the texture & color of the models and fade between two textures without problems, however I was wondering what the best way to simply fade a 3D object (blend it with the background) would be. I would assume that it wouldn't be done as fading between two textures (using lerp), since I want the object faded to the entire background, so there would be many different textures behind it.
I'm using the LPD3DXEFFECT as my effect class, DrawIndexedPrimitive as the drawing function in each pass, and I only have a single pass. I'm also using Shader Model 3, as this is an older project.
The only way that I thought it possible would be to simply get the color of the pixel before you apply any changes, and then do calculations on it with the color of the texture of the model to attain a faded pixel. However, after looking over the internet, it does not appear that it's actually possible to get the color of a pixel before doing anything to it with HLSL.
Is it even possible to do something like this using HLSL? Am I missing something that could assist me here?
Any help is appreciated!
Forgive me if I'm misunderstanding, but it sounds like you're trying to simulate transparency instead of using built-in transparency.
If you're trying to get the color of the pixels behind the object and want to avoid using transparency, I'd start by trying to use the last rendered frame as a texture, then reference that texture in your current shader. There may be some way to do it within the same frame - to force all other rendering to go first, then handle the one object - but I don't know it.
After a long grind, I finally found a very good workaround for my problem, and I will try to explain my understanding of it for anyone else that has a smillar issue. Thanks to Alexander Stewart for suggesting that there may be an in-built way to do it.
Method Description
Instead of taking care of the background fade in the HLSL pixel shader, there is another way to do it, using a method called Frame Buffer Alpha Blending (full MS Docs documentation: https://learn.microsoft.com/en-us/windows/win32/direct3d9/frame-buffer-alpha).
The basic idea behind this method is to provide a simple way of blending a given pixel that is to be rendered, with the existing pixel on the screen. There is a formula that is followed: FinalColor = ObjectPixelColor * SourceBlendFactor + BackgroundPixelColor * DestinationBlendFactor, all of these "variables" being groups of 4 float values, in the format (R, G, B, A).
How I Implemented it
Before doing anything with the actual shaders, in my Visual Studio C++ file I have to pass a few flags to my render device (I used LPDIRECT3DDEVICE9 as my device class). I had to set render states for both D3DRS_SRCBLEND and D3DRS_DESTBLEND, which are reffering to ObjectPixelColor and DestinationBlendFactor respectivelly in the formula above. These will be my factors that will be multiplying each one of my object and background pixel colors. There are many possible values that can be assigned to D3DRS_SRCBLEND and D3DRS_DESTBLEND, full list is available in the MS Docs link above, but in order to achieve what I wanted to (simply a way to fade an object into the background with an alpha number going from 0 to 1), I figured out the flags should be like this: SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA); SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);.
After setting these flags, before passing through my shaders & rendering, I just needed to set one more flag: SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);. I was also able to alternate between TRUE and FALSE here without changing anything else with no rendering problems (although my project was very simple, it will probably cause issues on larger projects). You can then pass any arguments you want, such as the alpha number, to the HLSL shader as a global variable (I did it using SetValue()).
Going back to my HLSL shader, after these changes, passing a color float4 variable taken from the tex2D() function from my pixel shader with an alpha value between 0 and 1 yielded the correct alpha, provided there aren't other issues (another issue that I had but hadn't realized at the time was the fact that my transparent object was actually rendering before the background, so I can only reccomend to check the rendering order when working on rendering projects).
I'm sure there could have probably been a better way of implementing this with the latest DirectX, but my compiler only supports Shader Model 3 and lower.
I'm using SceneKit on iOS and I have a geometry I want to render as a wireframe. So basically I want to draw only the lines, so no textures.
I figured out that I could use the shaderModifiers property of the used SCNMaterial to accomplish this. Example of a shader modifier:
material.shaderModifiers = [
SCNShaderModifierEntryPointFragment: "_output.color.rgb = vec3(1.0) - _output.color.rgb;"
]
This example apparently simply inverts the output colors. I know nothing about this 'GLSL' language I have to use for the shader fragment.
Can anybody tell me what code I should use as the shader fragment to only draw near the edges, to make the geometry look like a wireframe?
Or maybe there is a whole other approach to render a geometry as a wireframe. I would love to hear it.
Try setting the material fillMode to .lines (iOS 11+, and macOS 10.13+):
sphereNode.geometry?.firstMaterial?.fillMode = .lines
Now it is possible (at least in Cocoa) with:
gameView.debugOptions.insert(SCNDebugOptions.showWireframe)
or you can do it interactively if enabling the statistics with:
gameView.showsStatistics = true
(gameView is an instance of SCNView)
This is not (quite) an answer, because this a question without an easy answer.
Doing wireframe rendering entirely in shader code is a lot more difficult than it seems like it should be, especially on mobile where you don't have a geometry shader. The problem is that the vertex shader (and subsequently the fragment shader) just doesn't have the information needed to know where polygon edges are.
I know nothing about this 'GLSL' language I have to use for the shader fragment.
If you really want to tackle this problem, you'll need to learn some more about GLSL (the OpenGL Shading Language). There are loads of books and tutorials out there for that.
Once you've got some GLSL under your belt, take a look at some of the questions (like this one pulled from the Related sidebar) and other stuff people have written about the problem. (Note that when you're looking for mobile-specific limitations, OpenGL ES has the same limitations as WebGL on the desktop.)
With SceneKit, you have the additional wrinkle that you probably don't have a barycentric-coordinates vertex attribute (aka SCNGeometrySource) for the geometry you're working with, and you probably don't want to do the hard work of generating one. In OS X, you can use an SCNProgram with a geometryShader to add barycentric coordinates before the vertex/fragment shaders run — but then you have to do your own shading (i.e. you can't piggyback on the SceneKit shading like you can with shader modifiers). And that isn't available in iOS — the hardware there doesn't do geometry shaders. You might be able to fake it using texture coordinates if those happen to be lined up right in your geometry.
It might be easier to just draw the object using lines — try making a new SCNGeometry from the sources and elements of your original (solid) geometry, but when recreating the SCNGeometryElement, use SCNPrimitiveTypeLine.
I'd like to change my RenderTargets between SpriteBatch.Begin and SpriteBatch.End. I already know this works:
GraphicsDevice.SetRenderTarget(target1);
SpriteBatch.Begin()
SpriteBatch.Draw(...)
SpriteBatch.End()
GraphicsDevice.SetRenderTarget(target2);
SpriteBatch.Begin()
Spritebatch.Draw(...)
SPriteBatch.End()
But I'd really like to make this work:
SpriteBatch.Begin()
GraphicsDevice.SetRenderTarget(target1);
SpriteBatch.Draw(...)
GraphicsDevice.SetRenderTarget(target2);
Spritebatch.Draw(...)
SpriteBatch.End()
I've ever seen anybody doing this, but I didn't find any reason why.
EDIT: a little more about why I want to do this:
In my project, I use SpriteSortMode.Immediate (to be able to change the BlendState when I want), and I simply iterate through a sorted list of sprites, and draw them all.
But now I want to apply mutli passes shader on some sprites, but not all! I'm quite new to shaders, but from what I understood, I have to draw my sprite on an intermediate one using first pass, and the draw the intermediate sprite on the final render target using the second pass. (I'm using a gaussian blur pixel shader).
That's why I'd like to draw on the target I want, using the desired shader, without having to make a new begin/end.
The question is: Why do you want to change the render target there?
You won't have any performance improvements, since the batch would have to be split anyways when the render target (or any other render state) changes.
SpriteBatch tries to group the sprites by common attributes, for example the texture when SpriteSortMode.Texture is used. That means sprites sharing a texture will be drawn in the same draw call (batch). Having less batches can improve performance. But you can't change the GPU state during a draw call. So when you change the render target you are bound to use two draw calls anyways.
Ergo, even if the second example would work, the number of batches would be the same.
I am creating a custom button that needs to be able to glow to a varying degree
How would I use these pictures to make a button that 'glows' the diamond when it is pressed, and have this glow gradually fade back to inert state?
I want to churn out several different colours of diamond as well... I am hoping to generate all different coloured diamonds from the same stock images presented here.
I would like to get my head around the basic methods available, in enough detail that I can see each one through and make a decision which path to take...
My tangled efforts so far... ( I will delete all of this, or move it into possibly several answers as a solution unfolds... )
I can see 3 potential solution paths:
GL
it looks as though GL has everything it takes to get complete fine-grained control over the process, although functions exposed by core graphics come tantalisingly close, and that would save several hundred lines of code spread over a bunch of source files, which seems a bit ridiculous for such a basic task.
core graphics, and core animation to accomplish the blending
documentation goes on to say
Anything underneath the unpainted samples, such as the current fill color or other drawing, shows through.
so I can chroma-key mask the left image, setting {0,0,0} ie Black as the key.
this at least secures a transparent background, now I have to work on making it yellow instead of grey.
so maybe I could have started instead with setting a yellow back colour for my image context, then use some CGContextSetBlendMode(...) to imprint the diamond on the yellow, THEN use chroma-key masking to get a transparent background
ok, this covers at least getting the basic unlit image on-screen
now I could overlay the sparkly image, using some blend mode, maybe I could keep it in its current greyscale state, and that would just boost the colours of the original
only problem with this is that it is a lot of heavy real-time blending
so maybe I could pre-calculate every image in the animation... this is looking increasingly mucky...
Cocos2D
if this allows me to set the blend mode to additive blending then I could just composite the glowing image over the original image with an appropriate Alpha setting.
After digging through a lot of documentation, the optimal solution seems to be to use core graphics functions to get the source images into a single 2-component GL texture, and then use GL to blend between them.
I will need to pass a uniform value glow_factor into the shader
The obvious solution might seem to simply use
r,g,b = in_r,g,b * { (1 - glow_factor) * inertPixel + glow_factor * shinyPixel }
(where inertPixel is the appropriate pixel of the inert diamond etc)...
it looks like I would also do well to manufacture my own sparkles and add them over the top; a gem should sparkle white irrespective of its characteristic colour.
After having looked at this problem a little more, I can see several solutions
Solution A -- store the transition from glow=0 to glow=1 as 60 frames in memory, then load the appropriate frame into a GL texture every time it is required.
this has an obvious benefit that a graphic designer could construct the entire sequence and I could load it in as a bunch of PNG files.
another advantage is that these frames wouldn't need to be played in sequence... the appropriate frame can be chosen on-the-fly
however, it has a potential drawback of a lot of sending data RAM->VRAM
this can be optimised by using glTexSubImage2D; several frames can be sent simultaneously and then unpacked from within GL... in fact maybe the entire sequence. if this is so, then it would make sense to use PVRT texture compression.
iOS: playing a frame-by-frame greyscale animation in a custom colour
Solution B -- load glow=0 and glow=1 images as GL textures, and manually write shader code that takes in the glow factor as a uniform and performs the blend
this has an advantage that it is close to the wire and can be tweaked in all sorts of ways. Also it is going to be very efficient. This advantage is that it is a big extra slice of code to maintain.
Solution C -- set glBlendMode to perform additive blending.
then draw the glow=0 image image, setting eg alpha=0.2 on each vertex.
then draw the glow=1 image image, setting eg alpha=0.8 on each vertex.
this has an advantage that it can be achieved with a more generic code structure -- ie a very general ' draw textured quad / sprite ' class.
disadvantage is that without some sort of wrapper it is a bit messy... in my game I have a couple of dozen diamonds -- at any one time maybe 2 or 3 are likely to be glowing. so first-pass I would render EVERYTHING ( just need to set Alpha appropriately for everything that is glowing ) and then on the second pass I could draw the glowing sprite again with appropriate Alpha for everything that IS glowing.
it is worth noting that if I pursue solution A, this would involve creating some sort of real-time movie player object, which could be a very useful reusable code component.
I am using XNA for a 2D project. I have a problem and I don't know which way to solve it. I have a texture (an image) that is drawn to the screen for example:
|+++|+++|
|---|---|
|+++|+++|
Now I want to be able to destroy part of that structure/image so that it looks like:
|+++|
|---|---|
|+++|+++|
so that collision now will work as well for the new image.
Which way would be better to solve this problem:
Swap the whole texture with another texture, that is transparent in the places where it is destroyed.
Use some trickery with spriteBatch.Draw(sourceRectangle, destinationRectangle) to get the desired rectangles drawn, and also do collision checking with this somehow.
Split the texture into 4 smaller textures each of which will be responsible for it's own drawing/collision detection.
Use some other smart-ass way I don't know about.
Any help would be appreciated. Let me know if you need more clarification/examples.
EDIT: To clarify I'll provide an example of usage for this.
Imagine a 4x4 piece of wall that when shot at, a little 1x1 part of it is destroyed.
I'll take the third option:
3 - Split the texture into 4 smaller
textures each of which will be
responsible for it's own
drawing/collision detection.
It's not hard do to. Basically it's just the same of TileSet struct. However, you'll need to change your code to fit this approach.
Read a little about Tiles on: http://www-cs-students.stanford.edu/~amitp/gameprog.html#tiles
Many sites and book said about Tiles and how to use it to build game worlds. But you can use this logic to everything which the whole is compost from little parts.
Let me quick note the other options:
1 - Swap the whole texture with
another texture, that is transparent
in the places where it is destroyed.
No.. have a different image to every different position is bad. If you need to change de texture? Will you remake every image again?
2- Use some trickery with
spriteBatch.Draw(sourceRectangle,
destinationRectangle) to get the
desired rectangles drawn, and also do
collision checking with this somehow.
Unfortunately it's don't work because spriteBatch.Draw only works with Rectangles :(
4 Use some other smart-ass way I don't
know about.
I can't imagine any magic to this. Maybe, you can use another image to make masks. But it's extremely processing-expensive.
Check out this article at Ziggyware. It is about Deformable Terrain, and might be what you are looking for. Essentially, the technique involves settings the pixels you want to hide to transparent.
Option #3 will work.
A more robust system (if you don't want to be limited to boxes) would use per-pixel collision detection. The process basically works as follows:
Calculate a bounding box (or circle) for each object
Check to see if two objects overlap
For each overlap, blit the sprites onto a hidden surface, comparing pixel values as you go. If a pixel is already set when you try to draw the pixel from the second sprite, you have a collision.
Here's a good XNA example (another Ziggyware article, actually): 2D Per Pixel Collision Detection
Some more links:
Can someone explain per-pixel collision detection
XNA 2-d per-pixel collision
I ended up choosing option 3.
Basically I have a Tile class that contains a texture and dimention. Dimention n means that there are n*n subtiles within that tile. I also have an array that keeps track of which tiles are destroyed or not. My class looks like this in pseudo code:
class Tile
texture
dimention
int [,] subtiles; //0 or 1 for each subtile
public Tile() // constructor
subtiles = new int[dimention, dimention];
intialize_subtiles_to(1);
public Draw() // this is how we know which one to draw
//iterate over subtiles
for(int i..
for(int j ...)
if(subtiles[i,j] == 1)
Vector2 draw_pos = Vector2(i*tilewidth,
j*tileheight)
spritebatch.Draw(texture, draw_pos)
In a similar fashion I have a collision method that will check for collision:
public bool collides(Rectangle rect)
//iterate over subtiles
for i...
for j..
if(subtiles[i,j]==0) continue;
subtile_rect = //figure out the rect for this subtile
if(subtile_rect.intersects(rect))
return true;
return false;
And so on. You can imagine how to "destroy" certain subtiles by setting their respective value to 0, and how to check if the whole tile is destroyed.
Granted with this technique, the subtiles will all have the same texture. So far I can't think of a simpler solution.