How does opengl-es 2 assemble primitives?

Posted by stephelton on Game Development See other posts from Game Development or by stephelton
Published on 2011-06-29T23:17:04Z Indexed on 2011/06/30 0:31 UTC
Read the original article Hit count: 319

Filed under:

glsl

|

opengl-es2

Two things I'm quite confused about.

1) OpenGL ES 2.0 creates primitives before the vertex shader is invoked. Why, then, does it not automatically provide the vertex shader the position of the vertex?

2) OpenGL ES 2.0 supports glDrawElements(), but it does not support glEnableClientState() or GL_VERTEX_ARRAY, so how can this call possibly be used to construct primitives?

NOTE: this is OpenGL ES 2.0, NOT normal OpenGL!

Thanks!

© Game Development or respective owner

Related posts about glsl

How to debug a GLSL shader ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to debug a GLSL program but I don't know how to output intermediate result. Is it possible to make some debug traces (like with printf) with GLSL ? >>> More
How to update a uniform variable in GLSL

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi All, I am trying to get update the eye position in my shader from my appliaction but I keep getting error 1281 when I attempt this. I have no problems after the initialization just when i subsequently try to update the values. Here is my code: void GraphicsObject::SendShadersDDS(char vertFile… >>> More
GLSL check if fragment is on geometry

as seen on Stack Overflow - Search for 'Stack Overflow'
I am currently writing the positions of my geometry to the RGB channels of gl_FragColor and I would like to write 1.0 to the alpha channel if the fragment is part of geometry, and 0.0 if its empty. Is there a simple way to tell if a fragment is geometry or not? Maybe through gl_FragCoord.z? thanks >>> More
Implementing your own depth buffer with GLSL

as seen on Stack Overflow - Search for 'Stack Overflow'
I need a datastructure of the same size as the normal depth buffer and I need to be able to read from and write to it in a shader. Is this possible, and what does this datastructure look like? >>> More
Passing multiple Vertex Attributes in GLSL 130

as seen on Game Development - Search for 'Game Development'
(note this question is closely related to this one however I didn't fully understand the accepted answer) To support videocards in laptops I have to rewrite my GLSL 330 shaders to GLSL 130. I'm trying to do this but somehow I don't get vertex attributes to work properly. My 330 shaders look like… >>> More

Related posts about opengl-es2

Basic OpenGL ES2 (iPhone Simulator) question...

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi! I'm trying to modify the fragment shader which is part of the standard iPhone/XCode OpenGL ES template. I want to make it so that every other row of pixels is transparent. I have this code so far: varying lowp vec4 colorVarying; void main() { gl_FragColor = vec4(colorVarying.x, colorVarying… >>> More
Where are some good resources to learn Game Development with OpenGL ES 2.X

as seen on Game Development - Search for 'Game Development'
Background: From http://www.khronos.org/opengles/2_X/ OpenGL ES 2.0 combines a version of the OpenGL Shading Language for programming vertex and fragment shaders that has been adapted for embedded platforms, together with a streamlined API from OpenGL ES 1.1 that has removed any fixed functionality… >>> More
Fragment shader seems to floor() imprecisely

as seen on Game Development - Search for 'Game Development'
I'm trying to interpolate coordinates in my fragment shader. Unfortunately if close to the upper edge the interpolated value of fVertexInteger seems to be rounded up instead of beeing floored. This happens above approximately fVertexInteger >= x.97. Example: floor(64.7) returns 64.0 -- correct floor(64… >>> More
OpenGL 2 on Android: native window

as seen on Game Development - Search for 'Game Development'
According to OGLES specification, we have the following definition: EGLSurface eglCreateWindowSurface(EGLDisplay display, EGLConfig config, NativeWindowType native_window, EGLint const * attrib_list) More… >>> More
Android OpenGL ES 2 framebuffer not working properly

as seen on Game Development - Search for 'Game Development'
I'm trying to understand how framebuffers work. In order to achieve that, I want to draw a very basic triangle to a framebuffer texture and then draw the resulting texture to a quad on the default framebuffer. However, I only get a fraction of the triangle like below. LE: The triangle's coordinates… >>> More