Performance Guidelines for Artists and Designers

Here are some general guidelines for content creation and level design to improve performance.

For Artists

  • Minimize the number of elements per object.

  • Combine models to have a reasonable amount of triangles per element (e.g. 300+ per element).

  • Opaque materials are fastest due to having the best z buffer culling, masked are a bit slower, and translucent materials are slowest because of overdraw.

  • Limit UV seams and hard edges as it results in more vertices for the hardware. In the worst case, high poly meshes with hard edges result in 3 times more vertices than reported in modelling applications.

  • The vertex processing cost for skinned meshes is higher than for Static Meshes.

  • The vertex processing cost gets larger when adding morph targets or when using WorldPositionOffset. Texture lookups can be quite slow due to caching.

  • Tessellation adds quite a lot of extra cost and should be avoided when possible. Pretessellated meshes are usually faster.

  • Very large meshes can be split for better culling. This is for view culling, as light culling is usually done at a finer granularity.

  • Smaller texture formats result in faster materials (e.g. DXT1 is 4 bits per pixel, DXT5 is 8 bpp, ARGB uncompressed is 32 bpp).

  • Lower resolution textures can be faster (when magnified). Sometimes they can be even smoother, as bilinear filtering can result in more shades than the texture format can express.

  • Materials with few shader instructions and texture lookups run faster. To optimize materials, use Material Editor stats and the view mode ShaderComplexity.

  • Never disable mip maps if the texture can be seen in a smaller scale, to avoid slowdowns due to texture cache misses.

  • Some material expressions are more costly (sin, pow, cos, divide, Noise). The fastest expressions include: multiply, add, subtract, as well as clamp() when using 0 and 1.

  • Shading models have a cost: Unlit is fastest, Lit is what should be used mostly, and other models are more expensive.

For Level Designers

  • Limit the number of Stationary and Dynamic Lights.

  • Area light sources are a bit more expensive so avoid them where possible.

  • Adjust the draw distance on smaller objects to allow for better culling.

  • Verify LOD are setup with aggressive transition ranges. A LOD should use vertex count by at least 2x. To optimize this, check the wireframe, and solid colors indicate a problem. Using the Simplygon integration, it only takes minutes.

  • Try to combine lights that have a similar origin. For example, car head lights can use a single light with a light function to make it appear to be two lights.

  • Static lights are the fastest, Stationary lights are less optimal, and Dynamic lights are the most costly.

  • Limit the attenuation radius and light cone angle to the minimum needed.

  • Dynamic/Stationary point lights are the most expensive, directional lights are a little cheaper, and spot lights are best. Shadowmap generation cost scales with shadow casting objects' light frustum.

  • Light functions cost extra (actual cost depends on the material) and can prevent the light being rendered as a tiled light.

  • IES profiles cost extra (less than light functions) and can prevent the light being rendered as a tiled light. Do not use IES where spotlight cone angles could create the same effect.

  • Billboards, imposter meshes, or skybox textures can be used to efficiently fake detailed geometry.

  • Good level design takes occlusion culling into account (add visibility blockers for better performance). Use r.VisualizeOccludedPrimitives to check this.

  • Avoid Light Propagation Volumes or limit its cost by using the GIReplace material expression or disabling it on most objects.

  • Disable shadow casting where possible, either per object or per light.

  • Use ProfileGPU (Ctrl + Shift + ,) in the editor to get quick information on what is slow.

  • Decal performance cost scales with the number of pixels they cover.


CONSOLE: r.VisualizeOccludedPrimitives 1