# Tag Info

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). ...
• 1,444

### 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 ...

### How does the view-independence of radiosity increase the calculations involved?

Radiosity, by definition, handles only the diffuse component. You cannot 'limit' Radiosity to diffuse, because it already is handling just that diffuse component (remember - the diffuse lighting is ...
• 141
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 ...
• 3,616
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 ...
• 3,616
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### 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 ...
• 3,616

### 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 ...
• 1,950

### 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 ...
• 3,616

### 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 ...
• 1,541
### 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 ...