If there are different indexes for vertex coordinates and texture coordinates, then the vertex positions must be “duplicated”. The vertex coordinate and its attributes (like texture coordinate) form a tuple. Each vertex coordinate must have its own texture coordinates and attributes. You can think of a 3D vertex coordinate and a 2D texture coordinate as … Read more
[…] but can’t use it to index an array of samplers as expected because compiler sees it as “non-constant” […] In GLSL up to version 3.30 respectively GLSL ES up to version 3.00, the index of an array of texture samplers has to be a constant expression: GLSL 3.30 Specification – 4.1.7 Samplers (page 21) … Read more
I think you are reading correctly the only problem is that you are not linearize the depth from buffer back to <znear…zfar> range hence the ~1 value for whole screen due to logarithmic dependence of depth (almost all the values are very close to 1). I am doing this like this: double glReadDepth(double x,double y,double … Read more
Use quaternions (SLERP). Neither rotation matrices nor Euler angles are appropriate for interpolation. See 45:05 here (David Sachs, Google Tech Talk).
In a rendering, each mesh of the scene usually is transformed by the model matrix, the view matrix and the projection matrix. Projection matrix: The projection matrix describes the mapping from 3D points of a scene, to 2D points of the viewport. The projection matrix transforms from view space to the clip space, and the … Read more
This is rather basic knowledge that your favourite OpenGL learning resource should teach you as one of the first things. But anyway the standard OpenGL pipeline is as follows: The vertex position is transformed from object-space (local to some object) into world-space (in respect to some global coordinate system). This transformation specifies where your object … Read more
This should work: glEnable(GL_BLEND); // Use a simple blendfunc for drawing the background glBlendFunc(GL_ONE, GL_ZERO); // Draw entire background without masking drawQuad(backgroundTexture); // Next, we want a blendfunc that doesn’t change the color of any pixels, // but rather replaces the framebuffer alpha values with values based // on the whiteness of the mask. In … Read more
The output of a vertex shader is a four component vector, vec4 gl_Position. From Section 13.6 Coordinate Transformations of core GL 4.4 spec: Clip coordinates for a vertex result from shader execution, which yields a vertex coordinate gl_Position. Perspective division on clip coordinates yields normalized device coordinates, followed by a viewport transformation (see section 13.6.1) … Read more
From http://web.archive.org/web/20130416194336/http://olivers.posterous.com/linear-depth-in-glsl-for-real // == Post-process frag shader =========================================== uniform sampler2D depthBuffTex; uniform float zNear; uniform float zFar; varying vec2 vTexCoord; void main(void) { float z_b = texture2D(depthBuffTex, vTexCoord).x; float z_n = 2.0 * z_b – 1.0; float z_e = 2.0 * zNear * zFar / (zFar + zNear – z_n * (zFar – zNear)); } … Read more
The model, view and projection matrices are three separate matrices. Model maps from an object’s local coordinate space into world space, view from world space to camera space, projection from camera to screen. If you compose all three, you can use the one result to map all the way from object space to screen space, … Read more