Below are a number of useful tips about optimising materials for very large scatters. These tips were submitted by AForestProUser
who kindly allowed us to reproduce them here.
- Even though everyone recommends using geometry for leaves instead of opacity maps, it's not always possible nor the most efficient way of creating a plant. So if you're using opacities, or have purchased a model that uses them, turn off filtering for the opacity bitmaps. This is particularly true for still images.
- The amount of transparent areas should be minimised in the bitmap. To do this, even if you are going to use a simple plane as a leaf a texture projected from the top view, try to cut out the areas of the geometry where you don't see any texture. Although it'll double your poly count, the render will be faster. Here's an example, assuming you have the same alpha map:
- Not related to speeding up renders, but to avoid getting a halo/fringing around leaves that use opacity maps, create an alpha that is slightly smaller than the diffuse map. Alternatively, fill the background of the diffuse bitmap with a similar color as the texture.
- In Photoshop, when creating an alpha channel , avoid feathering or at least use a very tiny amount.
- Set the Reflection Max Depth to a low amount if you don't really need it to be that high, 1 will work fine in most circumstances. Either disable glossiness for midground/ background objects &/or disable tracing of reflections for background objects. This works extremely well with the new LOD object in Forest Pack.
- Avoid using Refraction and Opacity at the same time.
- If you are a V-Ray user, take a look at the Max transp. level and also Transp. cutoff under Global switches and adjust them accordingly.
- Not foliage specific but avoid overlapping geometry, especially in animations. If you have a messy model and don't want to fix it, then use the Secondary Ray Bias settings under Global switches. Usually a small value above 0 will do, like 0.001 .
- I sometime disable the filtering on all maps whether Opacity or not. That won't cause too many issues especially in stills. The same thing is true for Antialiasing Image filter options in V-ray. I tend to turn it off.
- Remove unused objects and assets from the scene. Also try to include only items that are visible at render-time. If it's not going to be seen and has no effect, then it shouldn't be there. (Unless it's used for shadows or reflections)
- Blend materials will slow thing down dramatically, try to avoid them as much as you can.
- Try to use as few lights as possible. Storing lights with Irradiance map is a great time saver option, but it has its drawbacks such as not being able to output that particular light in light select element. Similarly use light cache for glossiness, especially in scenes with lots of foliage and glossiness.
- Avoid V-Ray displacement where possible. Instead subdivide your geometry to an acceptable resolution and use Max's default Displace modifier. Works great for many scenes.
- Handling 1000 objects of 100 polys is more difficult for renderer than 10 object of 10000 polys.
- Try not to have your scene far from the origin. This is usually the case for imported models from other apps like AutoCAD or ArchiCAD.
- For background trees try to use bigger leaves(up to an acceptable range) which will result in lower polycounts. You may also be able to disable opacities for those as well.
- Remember if you are using X-refs there are options to merge materials and transformation.
- There's a new option in V-ray 3.1 which allows you to use different opacity modes for materials which will decrease the render time in scenes with lots of opacities.
- If a detail can't be seen, it shouldn't be there.
More to follow.
« Last Edit: February 18, 2015, 01:15:48 PM by Paul Roberts »