Comparing Texture Coordinate Systems: When To Use Generated, Unwrapped, Camera And Window Coordinates
Texture mapping is an essential technique in computer graphics and 3D modeling that allows images and textures to be mapped onto the surfaces of digital objects. The texture coordinates define how the 2D texture maps onto the 3D surface.
There are several texture coordinate systems available, each with their own use cases, advantages and limitations. Choosing the right system is crucial for mapping textures accurately and efficiently.
This article provides an in-depth comparison of the four main texture coordinate systems: generated coordinates, unwrapped coordinates, camera coordinates and window coordinates. We examine the algorithm and workflow behind each system, compare use cases and output, and provide code samples to demonstrate implementation.
What are Texture Coordinates and Why They Matter
Texture coordinates are 2D positions that map pixels from a texture image to vertices on a 3D model’s surface. They determine how the 2D texture wraps onto the 3D model.
Textures add realism and detail to 3D scenes. Complex materials like wood, metal and skin are difficult to model geometry-wise. But when texture maps are added to basic geometry, the results become highly realistic.
Texture mapping also saves modeling time. Quickly map an image of bricks to a wall rather than model each individual brick. The texture coordinates direct this mapping accurately.
For texture mapping to work properly, the texture coordinates must be precisely oriented to map the correct texel regions to mesh polygons. The different coordinate systems provide workflows of varying convenience and control over this mapping process.
Generated Coordinates: Automatic and Convenient
Generated coordinates are texture coordinates automatically created by modeling software like Maya, Blender and 3ds Max when simple mappings are needed.
UV mapping projects textures directly from the angle and direction of polygon surfaces. Mapping generation may utilize planar, cylindrical, spherical or other forms of projection based on mesh parameters and angle of view from texture image.
This automated system is very convenient – no unwrapping or coordinate editing needed. It also packs textures efficiently using the entire 0 to 1 UV space.
However, seams may be visible if projections intersect across mesh discontinuities. There is also no control over distortion or how the texture maps to the model.
Use generated coordinates for quick placeholder mappings, low-poly models and budget projects. Refine with unwrapped UVs if resources permit.
Generated Coordinate Workflows
In Maya, generated coordinates are computed automatically when a new texture is applied using Create UVs > Automatic Mapping. Cylindrical, spherical, planar and other projections can be specified.
Blender generates default UVs with each new model. The Smart UV Unwrap operation also auto-unwraps models effectively.
3ds Max generates mapping coordinates by default when applying a standard material with bitmap textures to an object using mapping types like Planar, Cylindrical, Spherical and Box.
Code Sample
//Maya generated UV mapping
polyCube;
autoProjectTexture; //automatically generate UVs for cube
fileTextureName = "bricks.jpg" //texture image
applyTexture(fileTextureName); //apply image texture to cube
Unwrapped Coordinates: Precise Manual Control
Unwrapped UVs refer to manually created texture coordinates by virtually cutting seams and unfolding polygons mesh surfaces to lay flat.
This unwrapping process allows textures to be mapped precisely across mesh surfaces according to concept art while minimizing stretching and distortion.
Manual unwrapping takes more time upfront but gives full control over the texture layout. It also reduces texture seam issues on complex organic models.
Use unwrapped coordinates when you need complete control over texture placement, accurate mapping of concept art or optimized usage of texture resolution.
Unwrapped UV Workflow
In Maya, manually unwrap with the Unfold operation. Insert edge loops to define seams, select polygon shells and layout in the UV texture editor. Optimize with tools like Layout and Relax.
In Blender, add seams to define UV islands, unwrap mesh pieces and pack islands into UV space. Use stretch, align and maximize tools to fine-tune fit.
3ds Max unwrapping workflow is similar. Use Peel, Unwrap and Flatten mapping operations combined with manually inserting seams and tweaking UV layouts.
Code Sample
//Manual mesh unwrapping in Maya
polySphere;
insertEdgeLoop; //add seam
setUvSeamOnEdge;
selectMeshFaces;
unfoldUV; //unwrap faces
layoutUV; //optimize layout
fileTexture = "earth.jpg"; //texture map
applyTexture(fileTexture);//map image to UVs
Camera Coordinates: Mapping Textures to Camera View
Camera coordinates map textures to mesh surfaces relative to the point of view of the scene camera. This keeps textures oriented accurately as models rotate and deform.
As geometry animates on screen, the texture coordinates update to remain aligned to the camera angle. This keeps textures stable – preventing unintended sliding or distortion.
Camera-mapped coordinates excel for texturing assets designed for film, video and real-time engines where on-screen motion is important. They help textures stay locked relative to camera angle.
Use camera coordinates for cutscenes, video game assets and film production where texture orientations should move realistically with on-screen geometry.
Camera Mapping Workflow
In Maya, camera mapping automatically generates UVs basing texture orientation on the scene camera’s transform and projection settings like lens angle and aspect ratio.
Blender utilizes the Render from View workflow to calculate texture coordinates using the active scene camera parameters.
3ds Max camera mapping works by enabling the View Coordinates modifier, which orients UVs to the viewport camera position.
Code Sample
//Camera-based UV generation in Maya
polyTorus;
cameraView = createCamera("textureCam");
cameraView.rotationX = 45; cameraView.focalLength = 35; //set up camera view
cameraMapUVs(cameraView); //generate camera UVs
fileTexture = "metal_plates.jpg";
applyTexture(fileTexture); //texture torus
Window Coordinates: Pixel-Perfect Texture Placement
Window coordinates map textures to mesh polygons relative to pixel positions in the viewport window. This snaps textures to precisely match surface features pixel-for-pixel.
Models stay perfectly aligned as they animate because the textures move with the mesh polygons from the constant viewport perspective.
Use window coordinates when textures, art or words need to lock precisely to geometry surfaces with no slippage – like a label on a moving bottle that must stay fixed.
Window Mapping Workflow
Maya’s Viewport 2.0 renderer and UV linking to viewport cameras allow pixel-accurate placement. 4-corner textures projected from matching view cameras lock geometry and textures together pixel-to-pixel.
Blender utilizes the Render from View plus a Texture Coordinate node with View mapping to acquire window coordinates for precision texturing.
In 3ds Max, the View Coordinates modifier snaps textures to the viewport perspective. A matching perspective view camera locks pixels in place.
Code Sample
//Window coordinate texture mapping in Maya
polyCylinder;
cameraViewA = createCamera("ViewCamA", viewport1); //link camera to viewport
cameraViewB = createCamera("ViewCamB", viewport2);
//create 4-corner view cameras to cover cylinder
cameraProjectUVs(cameraViewA, cameraViewB); //generate pixel-aligned UVs
fileTexture = "soda_label.jpg"; //texture to keep pixel-locked
applyTexture(fileTexture);
Comparing Use Cases and Results
In summary, here are the primary applications where each texture coordinate system excels:
- Generated coordinates – Fast/simple placeholder mappings
- Unwrapped UVs – Total control, complex texture layouts
- Camera coordinates – Texture stability with moving assets
- Window coordinates – Pixel-perfect precision texturing
The output results also vary. Generated and camera coordinates rely on software calculations for convenience. Unwrapped and window coordinates allow manually customization of mappings.
Remember that texture coordinates fundamentally control alignment of textures to surfaces. Choose thoughtfully based on your specific texturing needs.
Example Workflows and Sample Code
To help compare workflow, let’s examine test case of texturing a 3D logo model:
Generated and Unwrapped Comparison
With generated UVs, the software automatically projects textures without control, often resulting in mismatches, visible seams or uncontrolled stretching when surfaces bend and deform.
With manual unwrapping, the texture artist carefully flattens out mesh surfaces, enabling full control to map graphic details precisely.
Camera and Window Comparison
Camera mapping keeps the logo stabilized from any view angle, preventing distortion, but without pixel precision.
Window coordinates lock surfaces and textures together pixel-for-pixel as geometry animates, enabling clean sharp logos, text and labels.
Code Samples
Generated coordinates in Maya:
polyTorus;
autoProjectTexture(); //automatically generate UVs
textureLogo = "logo_graphic.jpg";
applyTexture (textureLogo); //apply texture automatically
Manual UV unwrapping workflow:
polyTorus;
insertEdgeLoops; //insert edge loops and seams
unwrapSections; //cut and flatten face sections
layoutUVs; //lay out faces
textureLogo = "logo_graphic.jpg";
placeTextureFaces(textureLogo); //manually fit logo graphic
Camera Mapping in Blender:
modelLogo = importModel("logo.obj");
addCamera("rotate_cam"); //add movable camera
mapCoordsToCamera(); //generate camera UVs
textureLogo = "logo_decal.png";
assignTexture(textureLogo); //keep logo locked to camera view
Window coordinates in Maya viewport:
modelLogo = polyCube();
linkCameraViewport(); //link camera to view
generateWindowUVs(); //generate pixel-precise UVs
textureLogo = "logo_decal.png";
snapTextureToSurface(textureLogo); //texture snaps pixel to pixel
