![]() This 8 cubic meter coordinate system used by clip space is known as normalized device coordinates (NDC). The center of the cube is the point (0,0,0). It is a cube two units on each side, with one corner at (-1,-1,-1) and the opposite corner at (1,1,1). The above graphic is a visualization of the clip space that all of the points must fit into. However, if a triangle straddles the border of this space then it is chopped up into new triangles, and only the parts of the new triangles that are in clip space are kept. Any data which extends outside of the clip space is clipped off and not rendered. In a WebGL program, data is typically uploaded to the GPU with its own coordinate system and then the vertex shader transforms those points into a special coordinate system known as clip space. These matrices are core to moving data around on the screen, and are concepts that transcend individual frameworks and engines. The sections below offer an in-depth look into the ideas behind and implementation of the model, view, and projection matrices. The view matrix is responsible for moving the objects in the scene to simulate the position of the camera being changed, altering what the viewer is currently able to see. A commonly used projection matrix, the perspective projection matrix, is used to mimic the effects of a typical camera serving as the stand-in for the viewer in the 3D virtual world. The projection matrix is used to convert world space coordinates into clip space coordinates. The first matrix discussed below is the model matrix, which defines how you take your original model data and move it around in 3D world space. This clip space is compressed down into a 2D space and rasterized into an image. ![]() This is a 2 unit wide cube, centered at (0,0,0), and with corners that range from (-1,-1,-1) to (1,1,1). These composed matrices ultimately move the original model data around into a special coordinate space called clip space. These matrices can be composed together and grouped in special ways to make them useful for rendering complicated 3D scenes. ![]() Individual transformations of points and polygons in space in WebGL are handled by the basic transformation matrices like translation, scale, and rotation.
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