OpenGL and GLSL are designed specifically to enable this sort of parallelization.įrom the OpenGL 4.6 specification, section 9.3.1: Even fragment shader invocations from separate draw calls. On a modern GPU, there will be thousands and thousands of fragment shader invocations running concurrently during rendering. Fragment shader invocations are generally not processed sequentially.
To achieve the level of performance necessary for real-time rendering, it is essential to take advantage of parallelism wherever possible.
In general, you cannot read from a texture image that is also being rendered to.
Is there in general a more elegant solution to this kind of problem? Now I wonder is there any way to tell OpenGL that those calls should truly be sequential and might there even be a way to do it with glDrawArraysInstanced to improve the performance? So I did rerun my code but this time with a bit of time passing between the calls and that seemed to have solved the issue. To me this pretty much looks like the two renderpasses aren't done sequentially, but in parallel. The second didn't (btw this is the same result as with the glDrawArraysInstanced): Result of second rendering Now while the first pass works as intended: Result of first rendering That however didn't really work so I split the glDrawArraysInstanced into 2 glDrawArrays and checked the 2 results. The first renderpass should draw the whole texture in grey (rgb = (0.5, 0.5, 0.5)) and the second should add another vec3(0.5) to that, so the result will be white. Now I call glDrawArraysInstanced with instancecount 2. So i draw into Framebuffer1, but also use the current colortexture attachement for the drawing. Vec3 text = texture(Framebuffer1, TexCoords).rgb I have 2 framebuffers: Default and Framebuffer1.Īnd give the colortexture attachment of Framebuffer1 as uniform "Fb1_cta" to the following fragment shader: out vec4 FragColor I found a way to do this is by having a shader which gets all the textures and renders their combination.īut to improve the performance wouldn't it be better to just have one shader and framebuffer, and then through instanced drawing the shader draws onto the framebuffer colortexture attachement it is using for drawing? I'm trying to basically "add" framebuffers, or better the colortexture attachmement of framebuffers.
0 kommentar(er)
