英文:
Ray tracer very noisy
问题
我正在实现一个光线追踪器。它运行在一个计算着色器内，将结果写入纹理。渲染器使用完美反射，即没有随机性。理论上不应该有噪音源。然而，实际上渲染的图像非常嘈杂。我对为什么会出现这种情况一无所知。
着色器代码：
光线与球体的相交检测：
HitInfo testSphereIntersect(vec3 rayOrigin, vec3 rayDir, Sphere s) {HitInfo h;h.didHit = true;vec3 translatedRayOrig = rayOrigin - s.position.xyz;float a = dot(rayDir, rayDir);float b = dot(translatedRayOrig, rayDir) * 2;float c = dot(translatedRayOrig, translatedRayOrig) - (s.radius * s.radius);float discriminant = (b * b) - (4 * a * c);if (discriminant < 0) {h.didHit = false;return h;}float t_0 = (-b - sqrt(discriminant)) / (2 * a);float t_1 = (-b + sqrt(discriminant)) / (2 * a);if (t_0 < 0 && t_1 < 0) {h.didHit = false;return h;}h.rayT = t_0 >= 0 ? t_0 : t_1;h.position = rayOrigin + rayDir * h.rayT;h.normal = normalize(h.position - s.position.xyz);return h;}
跟踪函数：
vec4 trace(vec3 rayDir, vec4 bgColour){vec3 rayOrigin = cameraPos;vec3 colour = vec3(0, 0, 0);HitInfo hit;uint sphereIndex;Material mat;float mult = 1.0f;for (int i = 0; i <= maxBounces; i++){hit = closestHit(sphereIndex, rayDir, rayOrigin);if (!hit.didHit){colour += bgColour.xyz * mult;break;}vec3 lightDir = normalize(vec3(-1, -1, -1));float intensity = max(dot(hit.normal, -lightDir), 0);mat = materials[spheres[sphereIndex].materialID];vec3 sphereCol = mat.kd.xyz;sphereCol *= intensity;colour += sphereCol * mult;rayOrigin = hit.position;rayDir = normalize(reflect(rayDir, hit.normal));mult *= 0.7f;}return vec4(colour, 1);}
这是找到最近的交点的函数：
HitInfo closestHit(out uint index, vec3 rayDir, vec3 rayOrigin){HitInfo minHit;minHit.rayT = 1.0 / 0.0;minHit.didHit = false;uint minIndex = -1;for (int i = 0; i < spheres.length(); i++){HitInfo h = testSphereIntersect(rayOrigin, rayDir, spheres[i]);if (!h.didHit)continue;if (h.rayT < minHit.rayT){minHit = h;minIndex = i;minHit.didHit = true;}}index = minIndex;return minHit;}
以下是光线生成代码：
vec3 getRayDir(float fov /* in degrees */, float aspectRatio) {vec2 texelCoord = gl_GlobalInvocationID.xy;vec2 ndc = vec2((texelCoord.x + 0.5) / (resolution[0]),(texelCoord.y + 0.5) / (resolution[1]));vec2 pixelCamera;pixelCamera.x = ((2 * ndc.x) - 1) * aspectRatio * tan(radians(fov / 2));pixelCamera.y = ((2 * ndc.y) - 1) * tan(radians(fov / 2));vec3 rayDir = normalize((lookAt * vec4(pixelCamera, -1.0f, 0)).xyz);return rayDir;}
英文:
So, I'm implementing a ray tracer. It runs inside a compute shader which writes the result onto a texture. The renderer uses perfect reflections, that is, there is no randomness. So, ideally, there should be no source of noise. However, the rendered image is, in fact, extremely noisy. I am clueless as to why this should be the case.
The shader code:
Ray-sphere intersection:
HitInfo testSphereIntersect(vec3 rayOrigin, vec3 rayDir, Sphere s) {HitInfo h;h.didHit = true;vec3 translatedRayOrig = rayOrigin - s.position.xyz;float a = dot(rayDir, rayDir);float b = dot(translatedRayOrig, rayDir) * 2;float c = dot(translatedRayOrig, translatedRayOrig) - (s.radius * s.radius);float discriminant = (b * b) - (4 * a * c);if (discriminant < 0) {h.didHit = false;return h;}float t_0 = (-b - sqrt(discriminant)) / (2 * a);float t_1 = (-b + sqrt(discriminant)) / (2 * a);if (t_0 < 0 && t_1 < 0) {h.didHit = false;return h;}h.rayT = t_0 >= 0 ? t_0 : t_1;h.position = rayOrigin + rayDir * h.rayT;h.normal = normalize(h.position - s.position.xyz);return h;}
The trace function:
vec4 trace(vec3 rayDir, vec4 bgColour){vec3 rayOrigin = cameraPos;vec3 colour = vec3(0, 0, 0);HitInfo hit;uint sphereIndex;Material mat;float mult = 1.0f;for (int i = 0; i <= maxBounces; i++){hit = closestHIt(sphereIndex, rayDir, rayOrigin);if (!hit.didHit){colour += bgColour.xyz * mult;break;}vec3 lightDir = normalize(vec3(-1, -1, -1));float intensity = max(dot(hit.normal, -lightDir), 0);mat = materials[spheres[sphereIndex].materialID];vec3 sphereCol = mat.kd.xyz;sphereCol *= intensity;colour += sphereCol * mult;rayOrigin = hit.position;rayDir = normalize(reflect(rayDir, hit.normal));mult *= 0.7f;}return vec4(colour, 1);}
This finds the closes hit:
HitInfo closestHIt(out uint index, vec3 rayDir, vec3 rayOrigin){HitInfo minHit;minHit.rayT = 1.0 / 0.0;minHit.didHit = false;uint minIndex = -1;for (int i = 0; i < spheres.length(); i++){HitInfo h = testSphereIntersect(rayOrigin, rayDir, spheres[i]);if (!h.didHit)continue;if (h.rayT < minHit.rayT){minHit = h;minIndex = i;minHit.didHit = true;}}index = minIndex;return minHit;}
And here is the ray generation code:
vec3 getRayDir(float fov /* in degrees */, float aspectRatio) {vec2 texelCoord = gl_GlobalInvocationID.xy;vec2 ndc = vec2((texelCoord.x + 0.5) / (resolution[0]),(texelCoord.y + 0.5) / (resolution[1]));vec2 pixelCamera;pixelCamera.x = ((2 * ndc.x) - 1) * aspectRatio * tan(radians(fov / 2));pixelCamera.y = ((2 * ndc.y) - 1) * tan(radians(fov / 2));vec3 rayDir = normalize((lookAt * vec4(pixelCamera, -1.0f, 0)).xyz);return rayDir;}
答案1
得分: -1
我借助这个回答解决了它：https://stackoverflow.com/a/35742512/18092120
显然，光线起始点离表面太近了，所以我所需要做的就是在反射光线的方向上微微偏移它。
英文:
I solved it with the help of this answer: https://stackoverflow.com/a/35742512/18092120
Apparently, the ray was starting too close to the surface, so all I had to do was offset it by a tiny amount in the direction of the reflected ray.
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