# Decimate To Quality > How to use the Decimate To Quality function in Asset Transformer Studio The **Decimate To Quality** function is used to efficiently reduce a model's polycount, **whilst preserving as much as possible its visual quality**. It works by smartly deleting vertices of the meshes (*Vertex removal* technique), using **quality criteria** to prevent smoothing artifacts and topological irregularities. ![Vertex removal technique](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_VertexRemoval.gif) The function is available from the [Optimize Mesh](../../user-interface/menu-bar/optimize-mesh-menu) menu. ## Parameters The algorithm uses a combination of 4 main parameters, which are geometrical tolerances to obtain the lightest model possible whilst keeping acceptable quality: | Parameter | Description | | --------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Surfacic tolerance** | Defines the maximum distance between vertices of the original model and resulting simplified surfaces. ![Surfacic tolerance](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_SurfacicTol.gif) | | **Lineic tolerance** | Defines the maximum distance between lineic vertices of the original model and resulting simplified lines. The `Lineic tolerance` preserves the boundaries of the original surface (where the edges are "sharp", or "hard"). ![Lineic tolerance](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_LineicTol.gif) *Thanks to the Lineic control, the **Decimate To Quality** function is particularly adapted for CAD models, which generally contain a lot of hard edges!* | | **Normal tolerance** | Defines the maximum angle existing between the original normals and those interpolated on the simplified surface. The `Normal tolerance` setting preserves the quality of how the light reacts on the surface of a mesh. Combined with the `Surfacic tolerance` setting, it will act as a quality controller, keeping polygons where the surface curvature is important. ![Normal tolerance](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_NormalTol.gif) | | **Texture Coordinates tolerance** | Preserves the UV (or Texture Coordinates) whilst decimating a mesh (0.01 is a good value). The higher the value, the more aggressive the decimation. Use `-1` to bypass this tolerance. ![UV tolerance](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_UVTol.gif) *Note: UV seams (like sharp edges) remain "significant" edges for the algorithm and are affected by the Lineic tolerance. To allow further polygon reduction, delete UVs prior to decimating.* | ## Presets | Preset | Description | | ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Low** (default) | The meshes will not be much decimated. Good for removing some useless polygons left behind after a [Remove Holes](/asset-transformer-studio/2026.5.0/api/python/algo_functions.md#removeholes) process for example. | | **Medium** | The meshes will be more decimated. Visible consequences might start showing but the result will be acceptable for meshes not visible from a reasonable distance. | | **Strong** | The meshes will be heavily decimated. They might show some artifacts: good to use for objects far from the camera. | ## Example Let's see a practical example with the Buggy model below (3DXML model, courtesy of *Dassault Systèmes*), which contains 140,846 triangles: ![Buggy model original](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example01.png)![Buggy model wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example02.png) > **Note:** > > Prior to performing a decimation, it's best to [repair](../../user-interface/menu-bar/mesh-menu) the model first. Set the parameter `Orient` to false if you are happy with the polygon face orientation. ### Surfacic Tolerance The surfacic tolerance is the maximum distance between the original model and the simplified one. The higher the tolerance, the lower the quality, but the higher the polygon reduction. Decimation with **surfacic tolerance** = 0.1 mm: the polycount is reduced to 66,636 but the quality is quite good: ![Surfacic 0.1mm](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example03.png)![Surfacic 0.1mm wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example04.png) Decimation with **surfacic tolerance** = 1 mm: the polygon count is now reduced to 7,155 but the quality is poor, and causes a lot of lighting problems: ![Surfacic 1mm](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example05.png)![Surfacic 1mm wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example06.png) To obtain a very low polycount without destroying visual quality, the algorithm can control **normal distortion** during the decimation process. ### Normal Distortion Tolerance The normal distortion tolerance is the maximum angle between a normal at each vertex of the original model and its corresponding normal on the simplified one. Decimation with **surfacic tolerance** = 1 mm and **normal distortion tolerance** = 5 degrees: the polycount is reduced to 9,525 with an almost imperceptible quality loss: ![Surfacic + Normal](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example07.png)![Surfacic + Normal wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example08.png) Finally, the high surfacic tolerance (1mm) produces a significant aliasing visible on sharp edges: ![Sharp edges aliasing](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example09.png)![Sharp edges aliasing wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example10.png) ### Lineic Tolerance This tolerance is equivalent to the surfacic tolerance but it is applied only on sharp edges (or hard edges) or on lines of interest. Decimation with **surfacic tolerance** = 1 mm, **normal distortion tolerance** = 5 degrees and **lineic tolerance** = 0.1 mm: the polycount is reduced to 13,126 with an almost imperceptible quality loss, even on sharp edges. The quality is better than using only a surfacic tolerance of 0.1 mm with a triangle count widely inferior (13,126 against 66,636): ![All three tolerances](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example11.png)![All three wireframe](/api/media?file=/asset-transformer-studio/2026.5.0/media/Pixyz_DecimateToQuality_Example12.png) ### Summary The best way to decimate a model using the **Decimate To Quality** function is to combine the 3 main parameters to obtain the lightest model while keeping an acceptable quality. | Parameters combination | Quality | Triangles | Reduction % | | :-----------------------------------------: | :-----: | :--------: | :---------: | | Surfacic 1mm | - | 7,155 | 94 | | Surfacic 0.1mm | + | 66,636 | 52 | | Surfacic 1mm + Normal 5° | ++ | 9,525 | 93 | | **Surfacic 1mm + Normal 5° + Lineic 0.1mm** | **+++** | **13,126** | **90** | | Original Mesh | ++++ | 140,846 | 0 | ### About the Texture coordinates tolerance As explained above, this parameter prevents the UVs from being too distorted at decimation. Decimation **without** texture coordinates tolerance: the wooden textures move because the underlying UVs get distorted: ![UV distortion](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_UVTol-02.gif) Decimation **with** texture coordinates tolerance = 0.001: the wooden texture moves far less because the underlying UVs are preserved: ![UV preserved](/api/media?file=/asset-transformer-studio/2026.5.0/media/ALGO_DecimateToQuality_UVTol-03.gif) ## API function parameters Check the [API Reference](/asset-transformer-studio/2026.5.0/api/python/algo_functions.md#decimate) to learn how to use this function in Python code. ## Related topics * [About Tessellation](../about-tessellation) * [Decimate To Target](./decimate-to-target.md) * [About 3D Models Types](../about-3d-models-types)