Android OpenGL ES 2.0：为具有相同片段着色器的对象设置唯一的颜色

Question

I have 6 columns in an Android OpenGL ES View. When the user touches the screen, a column glows a certain color. Initially, all the columns used the same glow color, but i'm trying to write code to give each column a unique glow color when touched.

The bug i'm noticing is that each column glow is still the same color, as if my call to set the glUniform is getting stuck on one color after being set the first time. The last color specified in my switch statement in setUniforms() is the color that all 6 columns use when touched, the colors should instead be different for each column.

Is there a bug in my Fragment Shader that causes all columns to incorrectly use case 5 's mGlowColorHandle value? Is the bug instead in my setUniforms method?

OpenGL_GLRenderer.java

public class OpenGL_GLRenderer implements GLSurfaceView.Renderer {

    @Override
    public void onDrawFrame(GL10 glUnused) {
        GLES20.glUseProgram(neckProgramHandle);
        setUniforms(neckProgramHandle);
        ...
    }

    private void setUniforms(int programHandle)
    {
        mGlowColorHandle = GLES20.glGetUniformLocation(programHandle, "stringGlowColor");           //column glow color

        //************************String Glow code*******************************
        //if user's touching the screen, make nearest string glow
        for (int i = 0; i< 6; i++) {
            if (stringGlowEffects[i] != null) {
                float top = orthoTop + (orthoBottom-orthoTop)*stringGlowEffects[i].y + scroller.getCurrentValue();
                GLES20.glUniform2f(mGlowPosHandles[i], stringGlowEffects[i].x, top);
                float aRandomFloat = (float) (Math.random() * 100);        //generate random number from 0-99
                float glowEffectScale = 1.0f + (aRandomFloat - 50.0f) / 300.0f;
                GLES20.glUniform1f(mGlowScaleHandles[i], glowEffectScale);      //ERROR HERE: case 5's color is displayed for every column
                switch (i){
                    case 0:
                        GLES20.glUniform4f(mGlowColorHandle,.0f, .0f, 1.0f, 1.0f);
                    case 1:
                        GLES20.glUniform4f(mGlowColorHandle,.0f, 1.0f, .0f, 1.0f);
                    case 2:
                        GLES20.glUniform4f(mGlowColorHandle,1.0f, .0f, .0f, 1.0f);
                    case 3:
                        GLES20.glUniform4f(mGlowColorHandle,.0f, 1.0f, 1.0f, 1.0f);
                    case 4:
                        GLES20.glUniform4f(mGlowColorHandle,1.0f, 1.0f, .0f, 1.0f);
                    case 5:
                        GLES20.glUniform4f(mGlowColorHandle,1.0f, .0f, 1.0f, 1.0f);
                }
            }
            else{
                GLES20.glUniform1f(mGlowScaleHandles[i], 0.0f);
            }
        }
    }
}

fragment_shader_neck.glsl

uniform sampler2D u_Texture;              // The input texture.
varying vec2 v_TexCoordinate;  // Interpolated texture coordinate per fragment.
uniform vec4 stringGlowColor;          // color of the string (column)

// The entry point for our fragment shader.
void main(){
    ...
    lowp vec4 fromTexture = texture2D(u_Texture, v_TexCoordinate);
    gl_FragColor = fromTexture + stringGlowColor*effectScale; 
}

Answer 1

You need a break statement after each call to GLES20.glUniform4f in your switch statement. When your program enters a switch statement, it jumps to the appropriate case label and continues until it hits a break statement or the end of the switch , even if that takes it past a different case label. This is sometimes useful, but mostly just confuses people.