Step 3: Rendering the Scene

After geometry has been initialized, it is time to render the scene. In order to render an object with texture, the texture must be set as one of the current textures. The next step is to set the texture stage states values. Texture stage states enable you to define the behavior of how a texture or textures are to be rendered. For example, you could blend multiple textures together.

The Texture sample project starts by setting the texture to use. The following code fragment sets the texture that the Microsoft® Direct3D® device will use to render with Direct3DDevice8.SetTexture.

g_D3DDevice.SetTexture 0, g_Texture

The first parameter that SetTexture accepts is a stage identifier to set the texture to. A device can have up to eight set textures, so the maximum value here is 7. This sample only has one texture and places it at stage 0. The second parameter is a pointer to a texture object. This sample uses the texture object that it created in its InitGeometry application-defined function.

The following code fragment sets the texture stage state values by calling the Direct3DDevice8.SetTextureStageState method.

g_D3DDevice.SetTextureStageState 0, D3DTSS_COLOROP, D3DTOP_MODULATE
g_D3DDevice.SetTextureStageState 0, D3DTSS_COLORARG1, D3DTA_TEXTURE
g_D3DDevice.SetTextureStageState 0, D3DTSS_COLORARG2, D3DTA_DIFFUSE
g_D3DDevice.SetTextureStageState 0, D3DTSS_ALPHAOP, D3DTOP_DISABLE

The first parameter that SetTextureState accepts is the stage index for the state variable to be set. This sample is changing the values for the texture at stage 0, so it puts a 0 here. The next parameter is the texture state to set. For a list of all valid texture states and their meaning, see CONST_D3DTEXTURESTAGESTATETYPE. The next parameter is the value to set the texture state to. The value that you place here is based on the texture stage state value that you are modifying.

After setting up the desired values for each texture stage state, the cylinder can be rendered with texture added to the surface.

Another way to use texture coordinates is to have them automatically generated. This is done by using a texture coordinate index (TCI). The TCI uses a texture matrix to transform the (x,y,z) TCI coordinates into (tu, tv) texture coordinates. In the Texture sample project, the position of the vertex in camera space is used to generate texture coordinates.

The first step is to create the matrix that will be used for the transformation. The code fragment for creating the matrix is shown below.

Dim mat As D3DMATRIX

mat.m11 = 0.25: mat.m12 = 0#:     mat.m13 = 0#: mat.m14 = 0#
mat.m21 = 0#:   mat.m22 = -0.25:  mat.m23 = 0#: mat.m24 = 0#
mat.m31 = 0#:   mat.m32 = 0#:     mat.m33 = 1#: mat.m34 = 0#
mat.m41 = 0.5:  mat.m42 = 0.5:    mat.m43 = 0#: mat.m44 = 1#

After the matrix is created, it must be set by calling SetTransform, as shown in the following code segment.

g_D3DDevice.SetTransform D3DTS_TEXTURE0, mat

The D3DTS_TEXTURE0 flag tells Direct3D to apply the transformation to the texture located at texture stage 0. The next step that this sample takes is to set more texture stage state values to get the desired effect. That is done in the code fragment below.

g_D3DDevice.SetTextureStageState 0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2
g_D3DDevice.SetTextureStageState 0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_CAMERASPACEPOSITION

The texture coordinates are set up and now the scene is ready to be rendered. Notice that the coordinates are automatically created for the cylinder. This particular setup gives the effect of the texture being laid over the rendering screen after the geometric shapes have been rendered.

For more information on textures, see Textures.

This tutorial has shown you how to use textures for surfaces. Tutorial 6: Using Meshes shows you how to use complex geometric shapes with meshes.