I’d like to extent on BDL’s answer. It is not only about the perspective interpolation. It is also about the clipping. The space the value gl_Position is supposed to be provided in is called clip space, and this is before the division by w. The (default) clip volume of OpenGL is defined in clip space … Read more
VAOs act similarly to VBOs and textures with regard to how they are bound. Having a single VAO bound for the entire length of your program will yield no performance benefits because you might as well just be rendering without VAOs at all. In fact it may be slower depending on how the implementation intercepts … Read more
You can’t easily communicate back to the CPU from within GLSL. Using glslDevil or other tools is your best bet. A printf would require trying to get back to the CPU from the GPU running the GLSL code. Instead, you can try pushing ahead to the display. Instead of trying to output text, output something … Read more
Rendering outlines, unless you render only a dozen characters total, remains a “no go” due to the number of vertices needed per character to approximate curvature. Though there have been approaches to evaluate bezier curves in the pixel shader instead, these suffer from not being easily antialiased, which is trivial using a distance-map-textured quad, and … Read more
OpenGL (and D3D. And Metal. And Mantle. And Vulkan) doesn’t support this because hardware doesn’t support this. Hardware doesn’t support this because, for the vast majority of mesh data, this would not help. This is primarily useful for meshes that are predominantly not smooth (vertices sharing positions but not normals and so forth). And most … Read more
When I compared your code with mine working engine I see these differences so try them one by one: texture format you are using: glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, screen_width, screen_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); so merging all your to: GL_COLOR_ATTACHMENT0: GL_RGBA,GL_RGBA,GL_UNSIGNED_BYTE GL_COLOR_ATTACHMENT1: GL_RGBA,GL_RGBA,GL_UNSIGNED_BYTE I am using: GL_COLOR_ATTACHMENT0 : GL_RGBA , GL_RGBA8 , GL_UNSIGNED_BYTE GL_DEPTH_ATTACHMENT : GL_DEPTH_COMPONENT, … 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).
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