# 3.9.3 Perspective Transformation, Clipping and Scissoring

## Utility Functions

guFrustum - Calculate a perspective projection matrix.
guFrustumF - Calculate a perspective projection matrix.
guLookAt - Calculate a 'lookat' view matrix.
guLookatF - Calculate a 'lookat' view matrix.
guOrtho - Calculate a positive projection matrix.
guOrthoF - Calculate a positive projection matrix.
guPerspective - Calculate a perspective drawing projection matrix.
guPerspectiveF - Calculate a perspective drawing projection matrix.

## GBI Commands

gSPViewport - Load the view port using the projection parameter.
gSPPerspNormalize - Normalize the perspective projection.
gSPClipRatio - Specify the relative ratio between clipping and scissoring.
gDPSetScissor - Specify the scissoring box using the screen coordinate.
gdSPDefLookAt - Load the x and y screen space coordinate directions to the lookat structure.

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Last Updated March, 1999