Questions tagged [diffuse]
The diffuse tag has no usage guidance.
25
questions
1
vote
1
answer
247
views
Confusion over Microfacet-based BRDFs and Normal Distribution Functions
Through reading various sources online, I've become a bit confused. I'll briefly outline what I think I do understand:
My understanding is that microfacet-based BRDFs assume there is always a perfect ...
- 229
0
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0
answers
93
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Ray tracing of a diffuse material sphere doesn't work, the sphere just shades black
I made this ray tracer in javascript to run on html with imageData. I have been using the book "Ray Tracing in One Weekend" as a reference (https://raytracing.github.io/books/...
- 101
0
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1
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209
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OpenGL old-style diffuse shading producing unexpected effects
Question:
What is going wrong with the shape of the contours of constant illumination in the below picture ?
Detail:
Although Lambertian shading might be ill-regarded because it exposes the hard edges ...
- 193
1
vote
1
answer
202
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Specular reflection with different viewing direction where reflection direction and viewing direction coincide
Suppose $P_1$ and $P_2$ two different points on surface. And let
$l$: be the light source direction,
$n$: normal vector
$r$: specular reflection direction
$v$: viewing direction .
In case 1 (at $P_1$...
- 211
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0
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136
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Contour-line looking artifact on diffuse irradiance map
I tried implementing my own diffuse irradiance map maker after reading Learn OpenGL > PBR > IBL > Diffuse Irradiance.
It takes an HDR image and makes six HDR cube map.
But It keeps making ...
- 111
1
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2
answers
659
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question about true Lambertian reflection in Ray tracing in one weekend
I have a question about Peter Shirley's Ray tracing in one weekend. In the True Lambertian Reflection section, when talking about rejection method, he said
This distribution scales by the cos^3(ϕ) ...
- 31
1
vote
1
answer
283
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Ray tracing Bug with Diffuse material
I am trying to do ray tracing in python (following the tutorial given in Ray Tracing in a weekend). Basically I am shooting rays from eye and the recursively bounce around, each time they hit ...
- 131
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48
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How to measure the reflectance of a material without using a Spectralon
I am trying to measure the reflectance% of a surface (it is made of Teflon and is very white). I am using a line spectrometer. I believe the piece can replace an expensive Spectralon for some ...
2
votes
1
answer
588
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Confusion around Lambert's Cosine Law in Ray Tracing in One Weekend
Peter Shirely's Ray Tracing in One Weekend presents the following function to calculate the color of a lambertian material (See chapter's 7 and 8):
...
- 123
1
vote
0
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112
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Oren-Nayar Reflectance
I'm trying to implement Oren-Nayar reflectance and I don't quite understand the Wikipedia article on it.
In the article, it has this diagram:
I can't figure out what $(\theta_i, \phi_i)$ and $(\...
- 111
3
votes
2
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1k
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Diffuse lighting calculations in ray-tracer
I am trying to write a ray-tracer. The lighting part is proving to work but not accurately. To debug I simplified the scene to a single sphere centered at the origin with a radius of 1 and a point ...
- 31
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216
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Factor of 2 converting radiance to irradiance
For a Lambertian surface, the radiance at a point is
$$L = \frac{\alpha}{\pi}\cos\theta_i E_0$$
If we have an infinite flat surface, albedo = 1, illuminated directly normal, then we get
$$L = \...
- 103
1
vote
0
answers
92
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How to automatically project texture from high poly mesh to low poly mesh?
I have two aligned meshes: I have exact mapping from each vertex of low poly mesh to surface of a high poly mesh. High poly (~100K vertices) mesh is non-manifold, low poly (~1K vertices) is manifold ...
- 161
7
votes
1
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Intuitively understanding conservation of energy for the Lambertian BRDF
The Lambertian BRDF is defined as $R / \pi$, where the division by $\pi$ is there to maintain conservation of energy. The derivation is provided here.
The maths makes sense, and I can understand ...
- 447
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1
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123
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Ringlike artifacts produced by rays bouncing off a light source
I recently set up a (very basic) ray-marched path-tracer, and I'm getting strange surface patterns on my area light [link]. I'm using known-valid analytical normals for the light's surface, and the ...
- 447