6
votes
Accepted
What is the purpose of the projected solid angle $dA^\perp$ term in the definition of Radiance?
Your main idea is more or less correct. The cosine hidden in the projected area measure $dA^\perp = dA\cos(θ)$ compensates the weakening of irradiance due to incident angle (the Lambert's cosine law). ...
- 1,474
5
votes
Which technique should be used for rendering under water images, Ray tracing or Radiosity?
Radiosity is only efficient for diffuse to diffuse rendering. Path tracing is more versatile on the type of light transport that could be computed. The main issue with underwater rendering is the ...
- 76
4
votes
Problem with definition of BSDF and radiance
Specular, Color, Fresnel
BSDF of purely specular surfaces is zero almost everywhere and infinite in one point [...] how do you know what is the reflectance of the surface at that point? From the ...
- 2,030
4
votes
Accepted
Radiance at a nearly perpendicular angle is almost infinite?
It's only more intense if $d\phi$ remains constant. However, for light source with constant luminance the flux is a function of $cos(\theta)$, i.e. depends on the light's angle of incidence with the ...
- 3,686
4
votes
Accepted
How to implement Texture Baking?
Yes, you should set the lightmap texture as the render target and use UV-coordinates as vertex position coordinates in your shader to bake lighting into lightmaps. This way you'll write the baked ...
- 3,686
3
votes
Accepted
What is Radiosity?
Radiosity is a way to calculate diffuse GI, i.e. every surface is assumed to be Lambertian surface without specular component. In the radiosity algorithm you split surfaces into small patches and ...
- 3,686
3
votes
Problem with definition of BSDF and radiance
The Rendering Equation
First thing first, the rendering equation in its solid angle formulation in vacuum is:
$$L(x,\omega) = L_e(x,\omega) + \int_{S^2} f(x, \omega_i, \omega_o) L(r(x,\omega), -\omega)...
- 2,561
2
votes
How to calculate attenuation and radiance in PBR? (point and directional lights)
You need to convert luminous flux (lumens, $lm$) to luminance ($\frac{lm}{m^2sr}$) for the rendering equation. For that you need to know the physical properties of the light source. For example ...
- 3,686
2
votes
How to calculate attenuation and radiance in PBR? (point and directional lights)
How should I define the radiance, if I have a directional light, for example the sun?
The radiance in physics has different definitions in different books. I will ...
- 1,613
2
votes
What is the purpose of the projected solid angle $dA^\perp$ term in the definition of Radiance?
Since you seem to want an explanation in terms of irradiance, consider both the radiance and irradiance definitions:
$$E = \frac{d\Phi}{dA}, \quad L = \frac{d^2\Phi}{d\omega dA^{\perp}}$$
We can ...
- 2,561
1
vote
How is Aperture and Pixel Size accounted for in calculating received power using ray tracing?
To understand whether your steps are correct you should compare to the mathematical formulation.
Step 1 is supposedly solving the rendering equation for some collection of initial rays
$$L_o(x_0, \...
- 2,561
1
vote
Albedo image map to color's Light Reflectance Value (LRV)
I am not aware of what LRV is and what is a usage of it. However, I can recommend using luma instead of simply averaging RGB values with equal weight:
https://en.wikipedia.org/wiki/Luma_(video)
https:...
1
vote
Radiance at a nearly perpendicular angle is almost infinite?
Remember radiance corresponds to a particular direction. When the equation is considering directions quasi parallel to the surface normal, the differential flux (the numerator) will typically be a ...
- 700
1
vote
Accepted
How to adapt diffuse/GI light mapper to directional light maps?
In the end, what I gleaned from the Valve paper, and what I found in an existing light mapper implementation, led me to the following conclusion:
When performing my final global illumination ...
- 315
1
vote
How to adapt diffuse/GI light mapper to directional light maps?
Take a look at Valve's paper on combining Radiosity and Normal Mapping. It had a lot of useful insights.
If I'm not mistaken, it looks to me like you're trying to compute normal mapping using the ...
- 198
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