Microsoft DirectX 9.0

Sphere Map Sample


The Sphere Map sample demonstrates an environment mapping technique called sphere mapping. Environment mapping is a technique in which the environment surrounding a 3-D object, such as the lights, are put into a texture map so that the object can have complex lighting effects without time-consuming lighting calculations.

Not all cards support all features for environment-mapping techniques such as cube mapping and projected textures. For more information about environment mapping, see Environment Mapping.


Source: (SDK root)\Samples\C++\Direct3D\EnvMapping\SphereMap

Executable: (SDK root)\Samples\C++\Direct3D\Bin

User's Guide

The following table lists the keys that are implemented. You can use menu commands for the same controls.

ENTERStarts and stops the scene.
SPACEBARAdvances the scene by a small increment.
F2Prompts the user to select a new rendering device or display mode.
ALT+ENTERToggles between full-screen and windowed modes.
ESCExits the application.

Programming Notes

Sphere-mapping uses a precomputed (at model time) texture map that contains the entire environment as reflected by a chrome sphere. The idea is to consider each vertex, compute its normal, find where the normal matches on the chrome sphere, and then assign that texture coordinate to the vertex.

Although the math is not complicated, this involves computations for each vertex for every frame. Microsoft?Direct3D?has a texture-coordinate generation feature that you can use to do this. The relevant render state operation is D3DTSS_TCI_CAMERASPACENORMAL, which takes the normal of the vertex in camera space and puts it through a texture transform to generate texture coordinates. Then you set up the texture matrix to do the rest. In this simple case, the matrix only has to scale and translate the texture coordinates to get from camera space (-1, +1) to texture space (0,1).

This sample uses common Microsoft DirectX?code that consists of programming elements such as helper functions. This code is shared with other samples in the DirectX software development kit (SDK). You can find the sample framework headers and source code in (SDK root)\DXSDK\Samples\C++\Common\Include and (SDK root)\DXSDK\Samples\C++\Common\Src.

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