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1500 questions
4
votes
2 answers
"whiteness" in center of bright colored lights - what is it called?
When a source of colored light is very bright, it's center appears white. What is the term I need to look for so I can implement this in my shader? I have added an image which is an example of what I mean. Obviously there is also some bloom going on…
AnnoyinC
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4
votes
0 answers
Project grid on 2d plane based on camera perspective
Unsure if this is the right network to post this, but maybe someone can help...
I'm working on a personal project where, with the help of AI, I want to automatically estimate the perspective of a given image.
I've been able to programatically…
Chris
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4
votes
1 answer
Deriving radiance from irradiance and intensity
I'm reading PBRT and am stuck in chapter 5.4 about radiometry. In particular:
We define the irradiance as the average density flux arriving at a surface with units $\frac{W}{m^2}$. So for a point light source, we have: $E = \frac{\Phi}{4 \pi r^2}$…
lyinch
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4
votes
1 answer
Gradient descent (Not ML) on arbitrary meshes
So I am doing a gradient descent like algorithm on the surface of a mesh and I just noticed something:
The above is the geodesic gradient (the distance to a single vertex)
Look at where the ear connects with the head and notice how the discretized…
Makogan
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4
votes
1 answer
How to interpolate vertices when clipping?
When we clip in homogeneous clip space, we have to generate a new vertex located at the intersection between the edge and the clip plane. We thus have to interpolate the $(x , y, z , w)$ position of both vertices to generate the new vertex position.…
Voko
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4
votes
3 answers
Why is there a difference between the CIE XYZ colour gamut vs CIE RGB?
Yet another question about colour space...
In my research on CIE XYZ system, I found that it is based on the CIE RGB colour matching experiments, and that because the RGB system needed occasional negative values, XYZ was developed in order to have…
FShrike
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4
votes
1 answer
What are the use cases for multiple render passes?
From what I understand of Vulkan, we have a render pass with its associated image resources and subpasses, and each subpass accesses those resources and may synchronise with previous subpasses to process the scene. In a 3D scene, we will have some…
FShrike
- 205
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- 8
4
votes
2 answers
Why is eye-based ray tracing preferred over light-based ray tracing?
It seems that virtually all path tracers use eye-based or view-based path tracing. That is, the light rays originate from the camera rather than the light source. The reason given for this everywhere I have seen online is that if one begins from the…
jheindel
- 163
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4
votes
1 answer
Perspective correct interpolation z-buffer
While I was deriving expressions for perspective-correct linear interpolation on triangles, I reached the conclusion that the interpolation may be kept linear only if view-space $Z$ is available. However, computing view-space $Z$ requires nonlinear…
lightxbulb
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3
votes
2 answers
Which perspective projection matrix to use
I've seen two different perspective projection matrices being used but I want to know which one of them is the best. I think that they both output the same but I'm not sure. So if anyone can help me select which one to use I would greatly appreciate…
Nixcc
- 33
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3
votes
2 answers
BRDF that interpolates between diffuse, glossy and reflective?
Is there a way to obtain a parametrized BRDF that smoothly interpolates between diffuse, glossy and mirror? For example, $\lambda = 0$ would be perfectly diffuse, $\lambda=0.5$ glossy and $\lambda = 1$ a perfect mirror. Linear interpolation seems…
vuoriov4
- 67
- 5
3
votes
1 answer
How to unproject cursor with orthographic projection
With perspective projection we can unproject screen space coordinates of the cursor to the near and far plane of the frustum and calculate the direction of the ray through the cursor.
Vector4 cScreen0 = Vector4(cursorNormX, cursorNormY, -1,…
Lenny White
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3
votes
2 answers
Why are texture coordinates often called UVs?
Is there some historical reason texture coordinates are often called UVs? I get that vertex positions are x, y, z but even OpenGL has TEXTURE_WRAP_S and TEXTURE_WRAP_T and GLSL has aliases so if texture coord is in a vec you can access it…
samanthaj
- 131
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3
votes
1 answer
How to compute the following integral over a polygon?
I am implementing an algorithm which requires me to compute the following integral,
$$\int_{Poly(P_i)}||P-P_i||^2 dP$$
where $P_i=(X_i, Y_i)$ is a point in 2D and $Poly(P_i)$ is a polygon containing $P_i$ (it is the Voronoi Cell of $P_i$ with a…
Student
- 133
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3
votes
1 answer
Interpreting Image Processing Math Equation
I am reading "Image Processing and Analysis" by Chan and Shen, c 2005 SIAM. They introduce some notation I'm not 100% sure how to interpret:
$$ u_0(x)=u(x)+n(x), x=(x_1,x_2) \in \Omega $$
They state $u_0$ represents a noisy image, $u$ is the clean…
Ron Jensen
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