我能够成功地将位图呈现到纹理上并在手机屏幕上显示它,没有问题。我现在想尝试从PNG文件中渲染另一个纹理覆盖在其上。覆盖的PNG文件包含一些透明(α)像素。
我可以将覆盖层渲染在背景纹理图像上方,但是当我这样做时,似乎透明像素被渲染为半透明黑色?除非黑色实际上来自我设置为黑色的纹理背景... 有人有什么建议吗,我可能做错了什么或者另一种实现所需效果的方法?
顶点着色器:
private final String vertexTextureShaderCode =
"attribute vec4 aPosition;"+ // Position of out Vertex
"attribute vec2 aTexPosition;"+ // Position of our texture contained in the vertex
"varying vec2 vTexPosition;"+ //
"void main(){"+
" gl_Position = aPosition;"+
" vTexPosition = aTexPosition;"+
"}";
片元着色器:
private final String fragmentTextureShaderCode =
"precision mediump float;" +
"uniform sampler2D uTexture;" + // Our Background Image ( Our uploaded image)
"uniform sampler2D uOverlay;"+ // Our Ovrelay image
"varying vec2 vTexPosition;" +
"void main() {" +
" vec4 colImage = texture2D(uTexture,vTexPosition);" +
" vec4 colOverlay = texture2D(uOverlay, vTexPosition);" +
" gl_FragColor = mix(colImage, colOverlay, 0.7);" +
"}";
绘制框架方法
public void drawOverlay(Context context,int resourceId){
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inScaled = false;
Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), resourceId,opts);
// Bind our TEXTURE_COORDS to the array
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,mTexturePointer[1]);
// Create the nearest filter TEXTURE_COORDS
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);
// Use Android GL Utils to specify a 2d TEXTURE_COORDS image from our bitmap
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
bitmap.recycle();
GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
GLES20.glUseProgram(mProgram);
// ENable bledning
// GLES20.glEnable(GLES20.GL_BLEND);
//
// // User SRC_OVE
// GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA);
// get handle to vertex shader vPosition member
mPositionHandle = GLES20.glGetAttribLocation(mProgram, "aPosition");
mTextureHandle = GLES20.glGetUniformLocation(mProgram, "uTexture");
mTextureOverlayhandle = GLES20.glGetUniformLocation(mProgram, "uOverlay");
mTexturePositionHandle = GLES20.glGetAttribLocation(mProgram, "aTexPosition");
GLES20.glVertexAttribPointer(mTexturePositionHandle, 2, GLES20.GL_FLOAT, false, 0, mTextureBuffer);
GLES20.glEnableVertexAttribArray(mTexturePositionHandle);
// ACTIVATING OUR FIRST TEXTURE, I.E our background image.
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTexturePointer[0]);
GLES20.glUniform1i(mTextureHandle,0);
// ACTIVATE OUR SECOND SECOND I.E our overlay
GLES20.glActiveTexture(GLES20.GL_TEXTURE1);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTexturePointer[1]);
GLES20.glUniform1i(mTextureHandle,1);
// Prepare the triangle coordinate data
GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, 0, vertexBuffer);
// enable a handle to the triangle vertice
GLES20.glEnableVertexAttribArray(mPositionHandle);
// clear the colors
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
GLES20.glDisable(GLES20.GL_DEPTH_TEST);
GLES20.glEnable(GLES20.GL_BLEND);
// User SRC_OVER
GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA);
// Draw the square
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, vertexCount);
// Disbale the vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
}
在我的片段着色器中使用混合方法是正确的吗?我应该将这两张图片绘制到一个纹理(sampler2D)中,而不是使用mix函数来处理两个sampler2D对象吗?如果是这样,我该怎么做呢?每次我尝试这样做时,前景纹理直接覆盖了背景纹理。