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Shading refers to the depiction of depth perception in 3D models (within the field of 3D computer graphics) or illustrations (in visual art) by varying the level of darkness. [1] Shading tries to approximate local behavior of light on the object's surface and is not to be confused with techniques of adding shadows, such as shadow mapping or ...
Shading can then be added to the facets, possibly with blending between the regions for a smoother display. Shading can also be static or dynamic. A lower quality of shading is typically used for dynamic shading, while high quality shading, with multiple light sources, textures, etc., requires a delay for rendering.
Gouraud shading (/ ɡ uː ˈ r oʊ / goo-ROH), named after Henri Gouraud, is an interpolation method used in computer graphics to produce continuous shading of surfaces represented by polygon meshes.
Phong shading is an improvement on Gouraud shading, and was one of the first computer shading models developed after the basic flat shader, greatly enhancing the appearance of curved surfaces in renders. Shaders are most commonly used to produce lit and shadowed areas in the rendering of 3D models.
(Note that although it looks like the bi-cubic interpolation approaches a sphere, an actual sphere is quadric.) Visual difference between sphere (green) and Catmull-Clark subdivision surface (magenta) from a cube. The Catmull–Clark algorithm is a technique used in 3D computer graphics to create curved surfaces by using subdivision surface ...
Drawing the scene with shadows can be done in several different ways. If programmable shaders are available, the depth map test may be performed by a fragment shader which simply draws the object in shadow or lighted depending on the result, drawing the scene in a single pass (after an initial earlier pass to generate the shadow map).
UV mapping is the 3D modeling process of projecting a 3D model's surface to a 2D image for texture mapping. The letters "U" and "V" denote the axes of the 2D texture because "X", "Y", and "Z" are already used to denote the axes of the 3D object in model space, while "W" (in addition to XYZ) is used in calculating quaternion rotations, a common ...
Phong shading improves upon Gouraud shading and provides a better approximation of the shading of a smooth surface. Phong shading assumes a smoothly varying surface normal vector. The Phong interpolation method works better than Gouraud shading when applied to a reflection model with small specular highlights such as the Phong reflection model.