glsl

I am hoping to implement a shader on a 2D OpenGL application. My plan is to render a scene to a framebuffer object, and then render that framebuffer object to the screen using a shader. Here is the scene, which I have drawn to a framebuffer object, and then to the screen from there. Using the arrow keys makes the moon move around (I am quite proud of it!) However, when I try to render the framebuffer object to the screen using my shader program, I get this: It is very sad. This fragment shader is one which I got from a tutorial , and I'm sure the problem has to be with the Uniform Variables.

So here is a previous question: How to implement a ShaderToy shader in three.js Tried to implement the steps from the link above into this code unsucessfully: three.js/blob/master/examples/webgl_shader.html So I replaced the original vertex shader and the origianl fragment shader so I got this code: <script id="vertexShader" type="x-shader/x-vertex"> varying vec2 vUv; void main() { vUv = uv; vec4 mvPosition = modelViewMatrix * vec4(position, 1.0 ); gl_Position = projectionMatrix * mvPosition; } </script> <script id="fragmentShader" type="x-shader/x-fragment"> uniform float iGlobalTime; uniform

When I look at the documentation of glMultiDrawElementsIndirect (or in the Wiki ) it says that a single call to glMultiDrawElementsIndirect is equivalent to repeatedly calling glDrawElementsIndirect (just with different parameters). Does that mean that gl_InstanceID will reset for each of these "internal" calls? And if so, how am I able to tell all these calls apart in my vertex shader? Background: I'm trying to draw all my different meshes all at once. But I need some way to known to which mesh the vertex, I'm processing in my vertex shader, belongs. Nicol Bolas The documentation says

Which is faster in GLSL: pow(x, 3.0f); or x*x*x; ? Does exponentiation performance depend on hardware vendor or exponent value? While this can definitely be hardware/vendor/compiler dependent, advanced mathematical functions like pow() tend to be considerably more expensive than basic operations. The best approach is of course to try both, and benchmark. But if there is a simple replacement for an advanced mathematical functions, I don't think you can go very wrong by using it. If you write pow(x, 3.0) , the best you can probably hope for is that the compiler will recognize the special case,

I have some vertex shader code somewhat like the following (this is a bit of simplified example): attribute vec2 aPosition; attribute vec4 aColor; varying lowp vec4 vColor; uniform vec4 uViewport; mat4 viewportScale = mat4(2.0 / uViewport.z, 0, 0, 0, 0, -2.0 / uViewport.w, 0,0, 0, 0,1,0, -1,+1,0,1); void main() { vec2 pos = aPosition; gl_Position = viewportScale * vec4(pos, 0, 1); vColor = vec4(aColor.rgb*aColor.a, aColor.a); } In particular, the viewportScale matrix is calculated from the uViewport uniform outside of the main function . Using this from a browser (WebGL), it seems to work fine