如何在OpenGLES中为多个对象上的多个纹理设置片段着色器？

Question

我尝试将纹理绑定到一个对象，将另一个纹理绑定到下一个对象。我在这里用stackoverflow询问了几乎相同的问题，但是那时候的区别是，我只有一个纹理和多个对象。How to bind texture just to one object in OpenGLES?它适用于一个纹理和多个对象，但是现在我有多个纹理和多个对象。我遵循了答案中的建议，但是我坚信这次的问题与片段着色器有关。

 @Override
public void onDrawFrame(GL10 gl) {
    GLES20.glClear(GL10.GL_COLOR_BUFFER_BIT);


    synchronized (mediaPlayerObject) {
        surfaceTextureMediaPlayer.updateTexImage();
        mediaPlayeUpdate = false;
    }


    vertexBuffer.position(0);
    GLES20.glVertexAttribPointer(aPositionLocation, POSITION_COMPONENT_COUNT, GLES20.GL_FLOAT, false, STRIDETEXTURE, vertexBuffer);
    vertexBuffer.position(TEXTURE_COMPONENT_COUNT);
    GLES20.glVertexAttribPointer(aTextureCoordinatesLocation, TEXTURE_COMPONENT_COUNT, GLES20.GL_FLOAT, false, STRIDETEXTURE, vertexBuffer);

    GLES20.glEnableVertexAttribArray(aPositionLocation);
    GLES20.glEnableVertexAttribArray(aTextureCoordinatesLocation);

    GLES20.glUniform1i(textureUnitLocation2, 1);
    GLES20.glActiveTexture(GLES20.GL_TEXTURE1);
    GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, textures[1]);

    GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 6);
    GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, 0);

    GLES20.glDisableVertexAttribArray(aPositionLocation);
    GLES20.glDisableVertexAttribArray(aTextureCoordinatesLocation);



    synchronized (camerObject) {
        surfaceTextureCamera.updateTexImage();
        cameraUpdate = false;
    }






    vertexBuffer2.position(0);
    GLES20.glVertexAttribPointer(aPositionLocation, POSITION_COMPONENT_COUNT, GLES20.GL_FLOAT, false, STRIDETEXTURE, vertexBuffer2);
    vertexBuffer2.position(TEXTURE_COMPONENT_COUNT);
    GLES20.glVertexAttribPointer(aTextureCoordinatesLocation, TEXTURE_COMPONENT_COUNT, GLES20.GL_FLOAT, false, STRIDETEXTURE, vertexBuffer2);

    GLES20.glEnableVertexAttribArray(aPositionLocation);
    GLES20.glEnableVertexAttribArray(aTextureCoordinatesLocation);

    GLES20.glUniform1i(textureUnitLocation, 0);
    GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, textures[0]);

    GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 6);
    GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, 0);

    GLES20.glDisableVertexAttribArray(aPositionLocation);
    GLES20.glDisableVertexAttribArray(aTextureCoordinatesLocation);

这里是片段着色器：

    #extension GL_OES_EGL_image_external : require
precision mediump float;
uniform samplerExternalOES u_Texture;
uniform samplerExternalOES b_Texture;

varying vec2 v_TextureCoordinates;

void main() {

    gl_FragColor = texture2D(u_Texture, v_TextureCoordinates) * texture2D(b_Texture, v_TextureCoordinates);
}

Answer 1

片段着色器中不需要第二个纹理采样器，因此删除b_Texture。将纹理对象绑定到纹理单元并将纹理单元的索引设置为均匀的纹理采样器就足够了：

#extension GL_OES_EGL_image_external : require
precision mediump float;
uniform samplerExternalOES u_Texture;

varying vec2 v_TextureCoordinates;

void main() {

    gl_FragColor = texture2D(u_Texture, v_TextureCoordinates);
}

绘制第一个对象：

GLES20.glUniform1i(textureUnitLocation, 1);
GLES20.glActiveTexture(GLES20.GL_TEXTURE1);
GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, textures[1]);

GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 6);

绘制第二个对象：

GLES20.glUniform1i(textureUnitLocation, 0);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GL_TEXTURE_EXTERNAL_OES, textures[0]);

GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 6);

注意，没有必要使用2个不同的纹理单位。在两种情况下都可以使用GL_TEXTURE0。