Simple divide by 0 error. The input radius was assumed to be safe
but is not when the user can scale it arbitrarly.
This also move the division out of the loop.
The SSS shader in Eevee has the following drawbacks (elaborated in {T79933}):
1. Glowing
2. Ringing. On low SSS jittering it is rendered a bunch of sharp lines
3. Overall blurriness due to the nature of the effect
4. Shadows near occlusions as in T65849
5. Too much SSS near the edge and on highly-tilted surfaces
{F9438636}
{F9427302}
In the original shader code there was a depth correction factor, as far as I can understand for fixing light bleeding from one object to another. But it was scaled incorrectly. I modified its scale to depend on SSS scale*radius and made it independent from the scene scale. The scale parameter (`-4`) is chosen so that it makes tilted surfaces to have visually the same SSS radius as straight surfaces (surfaces with normal pointed directly to the camera).
This depth correction factor alone fixes all the problems except for ringing (pt. 2). Because of float-point precision errors and irradiance interpolation some samples near the border of an object might leak light, causing sparkly or dashed (because of aliasing) patterns around the highlights. Switching from `texture()` to `texelFetch()` fixes this problem and makes textures on renders visually sharper.
An alternative solution would be to detect object borders and somehow prevent samples from crossing it. This can be done by:
1. Adding an `object_id` texture. I think it requires much more code changing and makes the shader more complicated. Again, `object_id` is not interpolatable.
2. Watch gradient of depth and discard samples if the gradient is too big. This solution depends on scene scale and requires more texture lookups. Since SSS is usually a minor effect, it probably doesn't require that level of accuracy.
I haven't notice it in practice, but I assume it can make visible SSS radius slightly off (up to 0.5 px in screen space, which is negligible). It is completely mitigated with render sampling.
Reviewed By: Clément Foucault
Differential Revision: https://developer.blender.org/D9740
- add the use of DRWShaderLibrary to EEVEE's glsl codebase to reduce code
complexity and duplication.
- split bsdf_common_lib.glsl into multiple sub library which are now shared
with other engines.
- the surface shader code is now more organised and have its own files.
- change default world to use a material nodetree and make lookdev shader
more clear.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D8306
This patch adds new render passes to EEVEE. These passes include:
* Emission
* Diffuse Light
* Diffuse Color
* Glossy Light
* Glossy Color
* Environment
* Volume Scattering
* Volume Transmission
* Bloom
* Shadow
With these passes it will be possible to use EEVEE effectively for
compositing. During development we kept a close eye on how to get similar
results compared to cycles render passes there are some differences that
are related to how EEVEE works. For EEVEE we combined the passes to
`Diffuse` and `Specular`. There are no transmittance or sss passes anymore.
Cycles will be changed accordingly.
Cycles volume transmittance is added to multiple surface col passes. For
EEVEE we left the volume transmittance as a separate pass.
Known Limitations
* All materials that use alpha blending will not be rendered in the render
passes. Other transparency modes are supported.
* More GPU memory is required to store the render passes. When rendering
a HD image with all render passes enabled at max extra 570MB GPU memory is
required.
Implementation Details
An overview of render passes have been described in
https://wiki.blender.org/wiki/Source/Render/EEVEE/RenderPasses
Future Developments
* In this implementation the materials are re-rendered for Diffuse/Glossy
and Emission passes. We could use multi target rendering to improve the
render speed.
* Other passes can be added later
* Don't render material based passes when only requesting AO or Shadow.
* Add more passes to the system. These could include Cryptomatte, AOV's, Vector,
ObjectID, MaterialID, UV.
Reviewed By: Clément Foucault
Differential Revision: https://developer.blender.org/D6331
This is an optimization / cleanup commit.
The use of a global ubo remove lots of uniform lookups and only transfert data when needed.
Lots of renaming for more consistent codestyle.
This option prevent from automatically blurring the albedo color applied to the SSS.
While this is great for preserving details it can bleed more light onto the nearby objects since the blurring will be done on pure "white" irradiance.
This issue is to be tackled in a separate commit.
This adds the possibility to simulate things like red ears with strong backlight or material with high scattering distances.
To enable it you need to turn on the "Subsurface Translucency" option in the "Options" tab of the Material Panel (and of course to have "regular" SSS enabled in both render settings and material options).
Since the effect is adding another overhead I prefer to make it optional. But this is open to discussion.
Be aware that the effect only works for direct lights (so no indirect/world lighting) that have shadowmaps, and is affected by the "softness" of the shadowmap and resolution.
Technical notes:
This is inspired by http://www.iryoku.com/translucency/ but goes a bit beyond that.
We do not use a sum of gaussian to apply in regards to the object thickness but we precompute a 1D kernel texture.
This texture stores the light transmited to a point at the back of an infinite slab of material of variying thickness.
We make the assumption that the slab is perpendicular to the light so that no fresnel or diffusion term is taken into account.
The light is considered constant.
If the setup is similar to the one assume during the profile baking, the realtime render matches cycles reference.
Due to these assumptions the computed transmitted light is in most cases too bright for curvy objects.
Finally we jitter the shadow map sample per pixel so we can simulate dispersion inside the medium.
Radius of the dispersion is in world space and derived by from the "soft" shadowmap parameter.
Idea for this come from this presentation http://www.iryoku.com/stare-into-the-future (slide 164).
Samples : pretty self explanatory.
Jitter Threshold : Reduce cache misses and improve performance (greatly) by lowering this value. This settings let user decide how many samples should be jittered (rotated) to reduce banding artifacts.
How to use:
- Enable subsurface scattering in the render options.
- Add Subsurface BSDF to your shader.
- Check "Screen Space Subsurface Scattering" in the material panel options.
This initial implementation has a few limitations:
- only supports gaussian SSS.
- Does not support principled shader.
- The radius parameters is baked down to a number of samples and then put into an UBO. This means the radius input socket cannot be used. You need to tweak the default vector directly.
- The "texture blur" is considered as always set to 1
