Question

我是OpenGl的新手，我想要实现的是给出一个从1.0到0.0的alpha纹理

我一直在搜索并且只找到“如何在图像中加载alpha”但我无法找到如何将alpha应用于对象

我已经尝试过：

gl.glEnable(GL10.GL_ALPHA_TEST);
alpha += 0.002f;
if(alpha > 1) alpha = 1f;
gl.glAlphaFunc(GL10.GL_EQUAL, alpha);

但它不起作用，我怎样才能给对象/纹理赋予alpha值（使fade效果）？

这是我的班级

public class Palabra {

public float posX = 0f;
public float posY = 0f;

public float scaleX = 2f;
public float scaleY = 2f;

public float alpha= 0.5f;

public State estado;

private FloatBuffer vertexBuffer, texBuffer; // Buffer for vertex-array

private float[] vertices = { // Vertices for a face
0.0f, 0.0f, 0.2f, // 0. left-bottom-front
2.1f, 0.0f, 0.2f, // 1. right-bottom-front
0.0f, 0.35f, 0.2f, // 2. left-top-front
2.1f, 0.35f, 0.2f // 3. right-top-front
};

float[] texCoords = { // Texture coords for the above face
0.00f, 0.0f, 1.0f, // A. left-bottom
1.00f, 0.0f, 1.0f, // B. right-bottom
0.00f, 0.2f, 1.0f, // C. left-top
1.00f, 0.2f, 1.0f // D. right-top
};

public enum State {
    MISS, NORMAL,GREAT,AWESOME,PERFECT;
}

public Palabra(int a) {
    // Setup vertex-array buffer. Vertices in float. An float has 4 bytes
    ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
    vbb.order(ByteOrder.nativeOrder()); // Use native byte order
    vertexBuffer = vbb.asFloatBuffer(); // Convert from byte to float
    vertexBuffer.put(vertices); // Copy data into buffer
    vertexBuffer.position(0); // Rewind

    // Setup texture-coords-array buffer, in float. An float has 4 bytes
    // (NEW)
     ByteBuffer tbb = ByteBuffer.allocateDirect(texCoords.length * 4);
     tbb.order(ByteOrder.nativeOrder());
     texBuffer = tbb.asFloatBuffer();
     texBuffer.put(texCoords);
     texBuffer.position(0);
     posX = (float) 0.00f;      
     switch(a)
     {
         case 0:
             posY = (float) 1f;
             break;
         case 1:
             posY = (float) 1.5f;
             break;
         case 2:
             posY = (float) 2f;
             break;
         case 3:
             posY = (float) 2.5f;
             break;
         case 4:
             posY = (float) 3f;
             break;
     }
}

public void draw(GL10 gl)
{
    gl.glMatrixMode(GL10.GL_MODELVIEW);
    gl.glLoadIdentity();
    gl.glPushMatrix();
    gl.glTranslatef(posX, posY, 0f);
    gl.glScalef(scaleX, scaleY, 0f);
    scaleX -= 0.02f;
    scaleY -= 0.02f;
    posX += 0.02f;
    if(scaleX < 1) 
    {
        scaleX = 1f;
        posX -= 0.02f;
    }
    if(scaleY < 1) scaleY = 1f;     

    gl.glMatrixMode(GL10.GL_TEXTURE);
    gl.glLoadIdentity();

    switch(this.estado)
    {
        case AWESOME:
            gl.glTranslatef(0.0f, 0.2f, 0f);
            break;
        case GREAT:
            gl.glTranslatef(0.0f, 0.4f, 0f);
            break;
        case NORMAL:
            gl.glTranslatef(0.0f, 0.6f, 0f);
            break;
        case MISS:
            gl.glTranslatef(0.0f, 0.8f, 0f);
            break;          
        case PERFECT:

            break;

    }



    gl.glFrontFace(GL10.GL_CCW); // Front face in counter-clockwise
                                    // orientation
    gl.glEnable(GL10.GL_CULL_FACE); // Enable cull face
    gl.glCullFace(GL10.GL_BACK); // Cull the back face (don't display)

    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
    gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); // Enable
                                                            // texture-coords-array
                                                            // (NEW)
    gl.glTexCoordPointer(3, GL10.GL_FLOAT, 0, texBuffer); // Define
                                                            // texture-coords
                            // buffer (NEW)

    gl.glEnable(GL10.GL_BLEND);
    gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);


    // front
    gl.glBindTexture(GL10.GL_TEXTURE_2D, TextureLoader.palabrasIDs[0]);

    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);

    gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); // Disable
                                                            // texture-coords-array
                                                            // (NEW)
    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glDisable(GL10.GL_CULL_FACE);
    gl.glDisable(GL10.GL_BLEND);
    gl.glPopMatrix();
}

}

Answer 1

我做到了！

这就是代码

gl.glEnable(GL10.GL_BLEND);
    gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
    gl.glColor4f(1f, 1f, 1f,alpha);
    alpha -= 0.002f;
    if(alpha < 0) alpha = 0f;

为对象OpenGL ES提供alpha

1 个答案: