Hi,

I successfully implemented the depth peeling in Jogl using modern OpenGL. I understood deeply most of the process except the blend step.

However I need to center my scene on a specific user action. This requires read the window z coordinate.

The problem is that the depth peeling just copy at the end the result in terms of color from a texture to the (back) framebuffer, depth values arent taken in account... In fact I get always 1.0 as window Z (clear depth value) if I try to retrieve the depth value at a specific mouse coordinate...

The core part is the following

Code :
private void renderDepthPeeling(GL3 gl3) {
        /**
         * (1) Initialize min depth buffer.
         */
        gl3.glBindFramebuffer(GL3.GL_FRAMEBUFFER, colorBlenderFboId[0]);
        gl3.glDrawBuffer(GL3.GL_COLOR_ATTACHMENT0);
 
        gl3.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        gl3.glClear(GL3.GL_COLOR_BUFFER_BIT | GL3.GL_DEPTH_BUFFER_BIT);
 
        gl3.glEnable(GL3.GL_DEPTH_TEST);
 
        dpInit.bind(gl3);
        {
            gl3.glUniform1f(dpInit.getAlphaUnLoc(), opacity);
 
            drawModel(gl3);
        }
        dpInit.unbind(gl3);
 
        /**
         * (2) Depth peeling + blending.
         */
        int layersNumber = (passesNumber - 1) * 2;
 
        for (int layer = 1; layer < layersNumber; layer++) {
 
            int currentId = layer % 2;
            int previousId = 1 - currentId;
 
            gl3.glBindFramebuffer(GL3.GL_FRAMEBUFFER, fboId[currentId]);
            gl3.glDrawBuffer(GL3.GL_COLOR_ATTACHMENT0);
 
            gl3.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
            gl3.glClear(GL3.GL_COLOR_BUFFER_BIT | GL3.GL_DEPTH_BUFFER_BIT);
 
            gl3.glDisable(GL3.GL_BLEND);
 
            gl3.glEnable(GL3.GL_DEPTH_TEST);
            {
                dpPeel.bind(gl3);
                {
                    gl3.glActiveTexture(GL3.GL_TEXTURE0);
                    gl3.glBindTexture(GL3.GL_TEXTURE_RECTANGLE, depthTextureId[previousId]);
                    gl3.glUniform1i(dpPeel.getDepthTexUnLoc(), 0);
                    {
                        gl3.glUniform1f(dpPeel.getAlphaUnLoc(), opacity);
                        drawModel(gl3);
                    }
                    gl3.glBindTexture(GL3.GL_TEXTURE_RECTANGLE, 0);
                }
                dpPeel.unbind(gl3);
 
                gl3.glBindFramebuffer(GL3.GL_FRAMEBUFFER, colorBlenderFboId[0]);
                gl3.glDrawBuffer(GL3.GL_COLOR_ATTACHMENT0);
            }
            gl3.glDisable(GL3.GL_DEPTH_TEST);
 
            gl3.glEnable(GL3.GL_BLEND);
            {
                gl3.glBlendEquation(GL3.GL_FUNC_ADD);
                gl3.glBlendFuncSeparate(GL3.GL_DST_ALPHA, GL3.GL_ONE, GL3.GL_ZERO, GL3.GL_ONE_MINUS_SRC_ALPHA);
 
                dpBlend.bind(gl3);
 
                gl3.glActiveTexture(GL3.GL_TEXTURE0);
                gl3.glBindTexture(GL3.GL_TEXTURE_RECTANGLE, colorTextureId[currentId]);
                gl3.glUniform1i(dpBlend.getTempTexUnLoc(), 0);
                {
                    drawFullScreenQuad(gl3);
                }
                dpBlend.unbind(gl3);
            }
            gl3.glDisable(GL3.GL_BLEND);
        }
 
        /**
         * (3) Final pass.
         */
        gl3.glBindFramebuffer(GL3.GL_FRAMEBUFFER, 0);
        gl3.glDrawBuffer(GL3.GL_BACK);
        gl3.glDisable(GL3.GL_DEPTH_TEST);
 
        dpFinal.bind(gl3);
        {
            gl3.glUniform3f(dpFinal.getBackgroundColorUnLoc(), 1.0f, 1.0f, 1.0f);
 
            gl3.glActiveTexture(GL3.GL_TEXTURE0);
            gl3.glBindTexture(GL3.GL_TEXTURE_RECTANGLE, colorBlenderTextureId[0]);
            gl3.glUniform1i(dpFinal.getColorTexUnLoc(), 0);
            {
                drawFullScreenQuad(gl3);
            }
            gl3.glBindTexture(GL3.GL_TEXTURE_RECTANGLE, 0);
        }
        dpFinal.unbind(gl3);
    }

What I am interested on should be in the first passage, where I do render the min depth buffer. I am thinking about just copying the texture linked at the depth_attachment into a temp texture. Then at the end, in the third passage, in the dpFinal program I could bind this temp texture too so that the fragment shader should just write into the Z component of the output fragment the right depth too..

I want to ask if this is feasible and in any case if you have a better idea about the solution

However here you find the whole code:

https://github.com/elect86/modern-jo...epthPeelingGL3