如何在多纹理对象后绘制具有漫反射纹理的对象

Question

我正在使用多重纹理绘制一个对象。这很好，但是当我仅使用漫反射纹理绘制其他对象时，该漫反射纹理会与先前的纹理绑定。我知道我必须停用默认以外的纹理单元，并且必须在 GL_TEXTURE0 处创建活动纹理单元，但它不起作用。

这是我的代码

glClientActiveTexture(GL_TEXTURE0); // first texture
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, stride, texCoordOffset);
glClientActiveTexture(GL_TEXTURE1); // second texture
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, stride, texCoordLightOffset);

// Enable 2D texturing for the first texture.
glActiveTexture(GL_TEXTURE0);
glEnable(GL_TEXTURE_2D);

// Enable 2D texturing for the second texture.
glActiveTexture(GL_TEXTURE1);
glEnable(GL_TEXTURE_2D);

// We are trying for the multi-textured lighting effect from the OpenGL
// ES 2.0 book, page  223, Figure 10-3. The relevant shader equation is
// basecolor * (lightcolor + 0.25), so we set the constant as a base colour
glColor4f(0.25f, 0.25f, 0.25f, 1.0f);


// Set the light map has the current texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,m_new_tex);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT,5.0f);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

// add the light map to the constant 0.25
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_ADD);
glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_TEXTURE);
glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_PREVIOUS);

// Now set the background map (bricks) and modulate (multiply)
glActiveTexture(GL_TEXTURE1);
// we'll keep this code here as _texSelection will never be our lightmap
glBindTexture(GL_TEXTURE_2D, m_sky);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 5.0f);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

/* Set the texture environment mode for this texture to combine */
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);

/* Set the method we're going to combine the two textures by. */
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_MODULATE);

/* Use the previous combine texture as source 0*/
glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_PREVIOUS);

/* Use the current texture as source 1 */
glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_TEXTURE);

/*
 Set what we will operate on, in this case we are going to use
 just the texture colours.
 */
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);


glBindBuffer(GL_ARRAY_BUFFER, drawable.VertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, drawable.IndexBuffer);

glDrawElements(GL_TRIANGLES, drawable.IndexCount, GL_UNSIGNED_SHORT, 0);

glDisable(GL_TEXTURE_2D);

对于简单的漫反射纹理，在绑定纹理之前我必须编写哪些命令？

任何其他示例代码都会有所帮助。

Answer 1

首先，您必须为每个未使用的纹理单元禁用纹理 (glDisable(GL_TEXTURE_2D))，您已经在执行此操作。当然，您还必须为未使用的纹理单元禁用纹理坐标数组，因此在第二个纹理单元处于活动状态时（在调用 glClientActiveTexture(GL_TEXTURE1) 之后）调用 glDisableClientState(GL_TEXTURE_COORD_ARRAY)。

当您完成多重纹理处理后，您当然必须调用glActiveTexture(GL_TEXTURE0) 和glClientActiveTexture(GL_TEXTURE0)。否则所有以下纹理操作都适用于纹理单元 1 而不是 0。

但是所有这些事情已经在我对你其他问题的回答中说明了。你读过吗？

编辑：顺便说一句，glTexParameter 更改的状态是按纹理对象存储的，而不是按单元存储的。所以你不需要每帧调用这些，创建纹理后一次就足够了。