android - Opengl es 2.0 试图将浮点值传递给 fragment 着色器 android

Question

如何将浮点值传递给 fragment 着色器？

这是我在安卓上的代码:

int aUseTexture = GLES20.glGetAttribLocation(program, "uUseTexture");

        GLES20.glUniform1f(aUseTexture, 1.0f);
        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

这是我的着色器:

String verticesShader =
        "uniform mat4 uScreen;\n" +    
        "attribute vec2 aPosition;\n" +
        "attribute vec3 aColor;\n" +
        "attribute vec2 aTexPos; \n" +
        "varying vec2 vTexPos; \n" + 
        "varying vec3 vColor;\n" +
        "void main() {\n" +
        " vTexPos = aTexPos; \n" +  
        " gl_Position = uScreen * vec4(aPosition.xy, 0.0, 1.0);\n" +
        "  vColor = aColor;\n" +
        "}";

      // Our fragment shader. Just return vColor.
      // If you look at this source and just said 'WTF?', remember
      // that all the attributes are defined in the VERTEX shader and
      // all the 'varying' vars are considered OUTPUT of vertex shader
      // and INPUT of the fragment shader. Here we just use the color
      // we received and add a alpha value of 1.
      String fragmentShader =
        "uniform float uUseTexture; \n" +
        "uniform sampler2D uTexture;\n" +
        "precision mediump float;\n"+
        "varying vec2 vTexPos; \n" +
        "varying vec3 vColor;\n" + 
        "void main(void)\n" +
        "{\n" + 
        " if ( uUseTexture != 1.0 ) \n" +
        "  gl_FragColor = vec4(vColor.xyz, 1); \n" +
        " else \n" +
        "  gl_FragColor = texture2D(uTexture, vTexPos); \n" +
        //"  gl_FragColor = vec4(vColor.xyz, 1);\n" +
        "}";

您可以在 fragment 着色器中看到 if 语句，这是我试图检查我是否传入 1.0 的语句，它应该做纹理，否则使用颜色。

Answer 1

您可能对“统一变量”使用了错误的函数调用。尝试 glGetUniformLocation() 如下:

int aUseTexture = GLES20.glGetUniformLocation(program, "uUseTexture"); 

此外，浮点测试 (uUseTexture != 1.0) 可能并不总是可靠的。您可能想要使用整数类型。