I’m currently developing a drawing app on iOS, with OpenGL ES 2.0 (I begin using it). I would like to reproduce textured brushes on my app. For that, I decided to use shaders (best choice?). At this stage, I have my textured brushes, but unfortunately, I also have some performance problems after few seconds…
Here is an overview of my app process:
I receive about 140 points each second.
Each time, on the draw function, I browse all of my points (points of contained on the Stroke class, which is contained on the layer) and I redraw it.
Code:
for (int strokeId = 0; strokeId < layer->strokesList.size(); strokeId++) {
Stroke* stroke = layer->strokesList.at(strokeId);
[…]
glVertexAttribPointer(mainProgram.positionSlot, 2, GL_FLOAT, GL_FALSE, 0, stroke->vertices.Position);
glVertexAttribPointer(mainProgram.colorSlot, 4, GL_FLOAT, GL_FALSE, 0, stroke->vertices.Color);
glDrawArrays(GL_TRIANGLES, 0, (int)(stroke->nbVertices));
[…]
}
I am opened to any suggestion to improve this drawing method, thank you!
Related
i have a question about a circle which has a texture mapping. My code works well but i have not antialised edges so it is not smooth and looks not good. I have read now about 3 hours and found some solutions but i don't know how can i implement them in my code. There were two solutions which sounds pretty good.
First was a blurry texture which should bind instead of a non blurry to have smooth edges.
Second add color vertices on the edges with opacity to have smooth edges. My currently draw function looks like this:
CC_NODE_DRAW_SETUP();
[self.shaderProgram use];
ccGLBindTexture2D( _texture.name );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
ccGLBlendFunc( _blendFunc.src, _blendFunc.dst);
ccGLEnableVertexAttribs( kCCVertexAttribFlag_Position | kCCVertexAttribFlag_TexCoords );
// Send the texture coordinates to OpenGL
glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, 0, _textCoords);
// Send the polygon coordinates to OpenGL
glVertexAttribPointer(kCCVertexAttrib_Position, 2, GL_FLOAT, GL_FALSE, 0, _triangleFanPos);
// Draw it
glDrawArrays(GL_TRIANGLE_FAN, 0, _numOfSegements+2);
I am currently using cococs2d version 3. I asked a similar question and found only the solution of enable the multisampling on cocos2d but this break my fps to 30.
So maybe there is someone how can help me.
I'm trying to render a waveform in an EAGLContext View, and I can't for the life of me get it to anti-alias. Is anything clearly wrong with my OpenGL Code? Is anymore information required?
glLineWidth( 0.4f);// - pass * 1.0f);
glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
glEnable(GL_LINE_SMOOTH);
glColor4f(1., 1., 1., 1.);
// Set up vertex pointer,
glVertexPointer(2, GL_FLOAT, 0, oscilLine);
// and draw the line.
glDrawArrays(GL_LINE_STRIP, 0, kDefaultDrawSamples);
Is anything clearly wrong with my OpenGL Code?
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
^^^^^^^^^^^^^^^^^^^^
Try changing this to GL_LINE_SMOOTH_HINT?
Also, since you're using the deprecated 1.x APIs you should use glGet with GL_LINE_WIDTH_RANGE and GL_LINE_WIDTH_GRANULARITY to verify that the 0.4 value is actually a supported width. You also need to ensure that the rendering target you've created has bits for an alpha channel. Can you add the context creation code?
Finally, it's not quite canon, but according to this article this mechanism of line smoothing doesn't work on iOS devices, though it apparently may on the simulator.
I am working hard on a new iOS game that is drawn only with procedurally generated lines. All is working well, except for a few strange hiccups with drawing some primitives.
I am at a point where I need to implement text, and the characters are set up to be a series of points in an array. When I go to draw the points (which are CGPoints) some of the drawing modes are working funny.
effect.transform.modelviewMatrix = matrix;
[effect prepareToDraw];
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 2, GL_FLOAT, 0, 0, &points);
glDrawArrays(GL_POINTS, 0, ccc);
I am using this code to draw from the array, and when the mode is set to GL_LINE_LOOP or GL_LINE_STRIP all works well. But if I set it to GL_POINTS, I get a gpus_ReturnGuiltyForHardwareRestert error. And if I try GL_LINES it just doesn't draw anything.
What could possibly be going on?
When you draw with GL_POINTS in ES2 or ES3, you need to specify gl_PointSize in the vertex shader or you'll get undefined behavior (ugly rendering on device at best, the crash you're seeing at worst). The vertex shader GLKBaseEffect uses doesn't do gl_PointSize, so you can't use it with GL_POINTS. You'll need to implement your own shaders. (For a starting point, try the ones in the "OpenGL Game" template you get when creating a new Xcode project, or using the Xcode Frame Debugger to look at the GLSL that GLKBaseEffect generates.)
GL_LINES should work fine as long as you're setting an appropriate width with glLineWidth() in client code.
I'm trying to get a game I made for iOS work in OSX. And so far I have been able to get everything working except for the drawing of some random generated hills using a glbound texture.
It works perfectly in iOS but somehow this part is the only thing not visible when the app is run in OSX. I checked all coords and color values so I'm pretty sure it has to do with OpenGL somehow.
glDisable(GL_TEXTURE_2D);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glBindTexture(GL_TEXTURE_2D, _textureSprite.texture.name);
glColor4f(_terrainColor.r,_terrainColor.g,_terrainColor.b, 1);
glVertexPointer(2, GL_FLOAT, 0, _hillVertices);
glTexCoordPointer(2, GL_FLOAT, 0, _hillTexCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)_nHillVertices);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnable(GL_TEXTURE_2D);
You're disabling the texture coordinate (and color) array along with the texturing unit, yet are binding a texture coordinate pointer.
Is this really what you intend to do?
Appearantly it was being drawn after all, only as a 1/2 pixel line. Somehow there is some scaling on the vertices in effect, will have to check my code.
I can't find much info on whether drawing from multiple vertex buffers is supported on opengl es 2.0 (i.e use one vertex buffer for position data and another for normal, colors etc). This page http://developer.apple.com/library/ios/#documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/TechniquesforWorkingwithVertexData/TechniquesforWorkingwithVertexData.html and listing 9.4 in particular implies you should be able to, but I can't get it to work on my program. Code for the offending draw call:
glBindBuffer(GL_ARRAY_BUFFER, mPositionBuffer->openglID);
glVertexAttribPointer(0, 4, GL_FLOAT, 0, 16, NULL);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, mTexCoordBuffer->openglID);
glVertexAttribPointer(1, 2, GL_FLOAT, 0, 76, NULL);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIndexBuffer->openglID);
glDrawElements(GL_TRIANGLES, 10788, GL_UNSIGNED_SHORT, NULL);
This draw call will stall or crash with EXC_BAD_ACCESS on the simulator, and gives very weird behavior on the device (opengl draws random triangles or presents previously rendered frames). No opengl call ever returns an error, and I've inspected the vertex buffers extensively and am confident they have the correct sizes and data.
Has anyone successfully rendered using multiple vertex buffers and can share their experience on why this might not be working? Any info on where to start debugging stalled/failed draw calls that don't return any error code would be greatly appreciated.
Access violations generally mean that you are trying to draw more triangles than you have allocated in a buffer. The way you've set up buffers is perfectly fine and should work, I would be checking if your parameters are set properly:
http://www.opengl.org/sdk/docs/man/xhtml/glVertexAttribPointer.xml
http://www.opengl.org/sdk/docs/man/xhtml/glDrawElements.xml
I think your issue is either that you've switched offset and stride in your glVertexAttribPointer calls, or you've miscounted the number of indices you're drawing
Yes, you can use multiple vertex buffer objects (VBOs) for a single draw. The OpenGL ES 2.0 spec says so in section 2.9.1.
Do you really have all those hard-coded constants in your code? Where did that 76 come from?
If you want help debugging, you need to post the code that initializes your buffers (the code that calls glGenBuffers and glBufferData). You should also post the stack trace of EXC_BAD_ACCESS.
It might also be easier to debug if you drew something simpler, like one triangle, instead of 3596 triangles.