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OpenGL Problems when moving from Nvidia to ATI card / GPGPU performance comparision
By
JoeJ
, in Graphics and GPU Programming
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By QQemka
Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
Let's go:
Heightmap  i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 015 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
Collisions  i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
Drawing aabb  problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
There were several more but i forgot/solved them at time of writing
Thanks in advance

By RenanRR
Hi All,
I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Gettingstarted/Camera).
I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
Vertex Shader:
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);
So, some doubts:
 Why use it like that?
 Is it okay to manipulate the camera that way?
in this way, are not the vertex's positions that changes instead of the camera?
 I need to pass MVP to all shaders of object in my scenes ?
What it seems, is that the camera stands still and the scenery that changes...
it's right?
Thank you

By dpadam450
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By Devashish Khandelwal
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By Andrey OGL_D3D
Hi all!
I try to use the Sun shafts effects via post process in my 3DEngine, but i have some artefacts on final image(Please see attached images).
The effect contains the following passes:
1) Depth scene pass;
2) "Shafts pass" Using DepthPass Texture + RGBA BackBuffer texture.
3) Shafts pass texture + RGBA BackBuffer texture.
Shafts shader for 2 pass:
// uniform sampler2D FullSampler; // RGBA Back Buffer uniform sampler2D DepthSampler; varying vec2 tex; #ifndef saturate float saturate(float val) { return clamp(val, 0.0, 1.0); } #endif void main(void) { vec2 uv = tex; float sceneDepth = texture2D(DepthSampler, uv.xy).r; vec4 scene = texture2D(FullSampler, tex); float fShaftsMask = (1.0  sceneDepth); gl_FragColor = vec4( scene.xyz * saturate(sceneDepth), fShaftsMask ); } final shader:
// uniform sampler2D FullSampler; // RGBA Back Buffer uniform sampler2D BlurSampler; // shafts sampler varying vec4 Sun_pos; const vec4 ShaftParams = vec4(0.1,2.0,0.1,2.0); varying vec2 Tex_UV; #ifndef saturate float saturate(float val) { return clamp(val, 0.0, 1.0); } #endif vec4 blendSoftLight(vec4 a, vec4 b) { vec4 c = 2.0 * a * b + a * a * (1.0  2.0 * b); vec4 d = sqrt(a) * (2.0 * b  1.0) + 2.0 * a * (1.0  b); // TODO: To look in Crysis what it the shit??? //return ( b < 0.5 )? c : d; return any(lessThan(b, vec4(0.5,0.5,0.5,0.5)))? c : d; } void main(void) { vec4 sun_pos = Sun_pos; vec2 sunPosProj = sun_pos.xy; //float sign = sun_pos.w; float sign = 1.0; vec2 sunVec = sunPosProj.xy  (Tex_UV.xy  vec2(0.5, 0.5)); float sunDist = saturate(sign) * saturate( 1.0  saturate(length(sunVec) * ShaftParams.y )); sunVec *= ShaftParams.x * sign; vec4 accum; vec2 tc = Tex_UV.xy; tc += sunVec; accum = texture2D(BlurSampler, tc); tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.875; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.75; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.625; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.5; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.375; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.25; tc += sunVec; accum += texture2D(BlurSampler, tc) * 0.125; accum *= 0.25 * vec4(sunDist, sunDist, sunDist, 1.0); accum.w += 1.0  saturate(saturate(sign * 0.1 + 0.9)); vec4 cScreen = texture2D(FullSampler, Tex_UV.xy); vec4 cSunShafts = accum; float fShaftsMask = saturate(1.00001  cSunShafts.w) * ShaftParams.z * 2.0; float fBlend = cSunShafts.w; vec4 sunColor = vec4(0.9, 0.8, 0.6, 1.0); accum = cScreen + cSunShafts.xyzz * ShaftParams.w * sunColor * (1.0  cScreen); accum = blendSoftLight(accum, sunColor * fShaftsMask * 0.5 + 0.5); gl_FragColor = accum; } Demo project:
Demo Project
Shaders for postprocess Shaders/SunShaft/
What i do wrong ?
Thanks!


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