Game Art Cheatsheet

Most common glitches in game art and how to solve them

Troubleshooting tips for mesh issues, lighting bugs, particles, transparency, physics. The solutions can be applied in Unity, Unreal Engine, Godot and most other game engines.

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Content Troubleshooting

Geometry

Name	Symptom	Cause	Solutions
Aliased lines	Thin geo like cables or fences jitters, disappears	Geometry is thinner than a single pixel	– Make LODs with thicker geo, different texture – Blend to a solid texture at far distance – Use a different anti-aliasing algorithm
Flipped normals	Mesh is inverted or partially invisible	Back faces of triangles are hidden by default (backface culling)	– Flip (reverse) vertex normals to face outside – If both sides needed, enabled two-sided rendering in material
Import scale	Model is huge or tiny after importing	Different editors use 1 cm or 1 m as base unit	-Make sure to follow correct physical dimensions when modelling – Set import or export scale to 0.01 or 100x
Temporal anti-aliasing	Ghosting. Meshes leave blurry trail when moving	Temporal smoothing algorithms combine multiple frames over time for high quality	– Make sure game keeps good, stable framerate, high resolution – If using vertex displacement in shader, add motion vectors support – For stability but lower quality, switch to FXAA anti-aliasing
Z-Fighting	Flickering polygons	Multiple polys have equal Z-depth in the same pixel	– Make sure no polygons overlap on the same plane – Increase near clip distance in camera
Split edges	Holes appear in animated mesh	Vertices have two modes: shared or split	– Merge vertices in your 3d software – Lock vertex normals instead of physically splitting edges – Use auto smooth groups
Visibility culling	Mesh or particle system disappearing from certain positions	Frustum or occlusion culling hides objects by their bounding boxes	– Check if occluders (geometry) are correct – Increase bounding box size

Materials

Name	Symptom	Cause	Solutions
Bilinear mipmap filtering	Blurry textures at oblique angles	Bilinear filtering in perspective projection underestimates required mipmap level of a texture	– Use anisotropic texture filtering, if performance tradeoff is acceptable
sRGB vs linear	Textures are too dark or washed out after import, or roughness is wrong	Textures come in (at least) two formats: linear color or sRGB. Linear is used for data, while sRGB for human-readable color	– In texturing programs, export albedo/diffuse as sRGB – In game engine, enable sRGB in albedo/diffuse textures – Disable sRGB (use linear) for data (roughness, masks)
Normal Y-axis sign	Normal map looks inverted	Some engines expect Y+ axis to mean “down”, while others consider it “up”	– Invert green channel of normal map -In Unreal, tick Flip Green Channel in texture
Aliasing	Moire patterns, bloom flickering	Resolution is not dense enough to represent (aka sample) the content	– Use smoother patterns in textures – Add soft radius to light sources – Blend to smoother texture by distance – Use different anti-aliasing algorithm
Alpha bleeding	White edges in textures with transparency	Alpha compositing	– In Substance Painter, use Dilation mode when exporting -In Photoshop, fill the background by selecting alpha mask, inverting selection and use Fill > Content Aware – Respect premultiplied alpha in shaders
Hard normals on foliage	Flat shading on foliage models, harshly disconnected from terrain	Foliage mesh, made of big flat planes, is interpreted too literally by lighting	– Use manually edited, up-pointing vertex normals – Read normal from terrain
Negative or NaN color	Black or deeply saturated squares on screen	Pixel’s color value is negative or not a number. This corrupts some algorithms (bloom)	– Check for division-by-zero in shaders – Clamp values to [0,1] in shaders
Edge bleeding	Colors from another island of UV space bleeding into the borders of given one	Bilinear texture filtering picks up information from neighboring texels, as it’s unaware of UV seams or image atlas items	– Increase margins between UV islands – Add 1 pixel of space between items in tileset/atlas – In Substance Painter, use Dilation mode when exporting
Banding in display	Stepped gradients on screen	Transition between certain colors can’t be represented, due to display’s color precision	– Add some film grain – Use dithering – Check if your post-process stack has HDR until very end
Banding in textures	Stepped gradients in textures	Lossy compression can’t represent subtle gradient	– Use more contrast in your source textures (e.g. stronger normal map), then reduce it in shader
Half precision	Pixelated procedural materials on mobile	Mobile devices optimize some values by storing them in 16 bits instead of 32	– Make your effects less dependent on precision (smooth flow maps, bigger features on texture) – Use modulo (%, fmod) on final time and UVs – Force full precision on variable

Transparency

Name	Symptom	Cause	Solutions
Bad sorting of polygons	Triangles of meshes or particles appear in wrong order	Game engines employ per-object sorting instead of per-triangle, for speed	– Split big objects into smaller ones – Move pivot closer to center of mesh – Use dithered opacity or cutout alpha for semi-solid objects – Hack: change draw priority (render queue) of shader
Depth of field vs. transparents	Transparent objects are not affected by depth of field	DoF reads the depth of the scene to perform blur. Translucent materials don’t write single depth	– Use cutout alpha (masked opacity) instead – In Unreal, enable Separate Translucency in material- Sometimes you can’t avoid it

Lighting

Name	Symptom	Cause	Solutions
Lightmap bleeding	Dark or wrong mesh edges	Bilinear filtering picks up information from neighboring texels	– Increase margins between UV islands – Increase mesh’s lightmap resolution
Shadow acne	Stepped shadows at certain angles	Shadow map’s resolution is not enough to represent the continuous surface	– Play with shadow bias parameter in light’s settings – Increase shadow map resolution
Missing reflection probes	Black reflections on metals	Lack of reflection sources	– Make sure at least 1 reflection probe covers every area in the scene
Movable SkyLight (UE4)	Black reflections on metals	SkyLight or all reflection probes have Mobility set to Movable	– Change their Mobility to Static
Overlapping polygons	Black spots in lightmaps	Multiple triangles are baked to the same texel	– Make sure no UV islands overlap – Remove any overlapping geo in mesh & level – Check for duplicate objects in level
Dynamic lights limit	Flickering lights	Renderer reached a limit of light sources affecting the same pixel	– Reduce # of lights overlapping in that place (change radius, move, delete) – Use static (baked) lights instead

Animation

Physics

Contributing

If you want something added or fixed, just add a new issue on GitHub.
I welcome pull requests too! (though quality is expected)

Credits

Oskar Świerad of Tech Art Aid is the original author and current maintainer.
Huge thanks to contibutors of examples from the Unity, Unreal Reddit threads and Twitter.

License

Feel free to share, copy, print and modify the document, under the terms of Apache License 2.0.