java - JOGL 2.0, render depth buffer to texture -

i trying implement simple shadow mapping technique in jogl 2.0 , struggle rendering depth values texture. maybe doing wrong weird rendering scene in color works properly. have found similar question here @ stackoverflow, asked here: render depth buffer texture using frame buffer

and problem solved calling

gl.gldrawbuffer(gl2.gl_none); gl.glreadbuffer(gl2.gl_none); 

however, not in case. when render scene in texture in color normally, function works properly. here result:

however, after trying render depth values, renders white color (and doesn't correspond scene @ all)

---- updated code, working now:

private void initializefbo3(gl2 gl) {  //create frame buffer gl.glgenframebuffers(1, framebufferid, 0); gl.glbindframebuffer(gl2.gl_framebuffer, framebufferid[0]);  // ------------- depth buffer texture -------------- gl.glgentextures(1,depthbufferid,0); gl.glbindtexture(gl2.gl_texture_2d, depthbufferid[0]);  gl.glteximage2d(gl2.gl_texture_2d,          // target texture type         0,                                  // mipmap lod level         gl2.gl_depth_component,         // internal pixel format                                             //gl2.gl_depth_component         shadowmapwidth,                     // width of generated image         shadowmapheight,                    // height of generated image         0,                          // border of image         gl2.gl_depth_component,     // external pixel format          gl2.gl_unsigned_int,        // datatype each value         null);  // buffer store texture in memory  //some parameters gl.gltexparameteri(gl2.gl_texture_2d, gl2.gl_texture_min_filter, gl2.gl_nearest); gl.gltexparameteri(gl2.gl_texture_2d, gl2.gl_texture_mag_filter, gl2.gl_nearest); gl.gltexparameteri(gl2.gl_texture_2d, gl2.gl_texture_wrap_s, gl2.gl_clamp_to_edge); gl.gltexparameteri(gl2.gl_texture_2d, gl2.gl_texture_wrap_t, gl2.gl_clamp_to_edge);        //attach 2d texture fbo gl.glframebuffertexture2d(gl2.gl_framebuffer,         gl2.gl_depth_attachment,         gl2.gl_texture_2d,         depthbufferid[0],0);  gl.glbindtexture(gl2.gl_texture_2d, 0);  //disable color buffer //https://stackoverflow.com/questions/12546368/render-the-depth-buffer-into-a-texture-using-a-frame-buffer gl.gldrawbuffer(gl2.gl_none); gl.glreadbuffer(gl2.gl_none);  //set pixels ((width*2)* (height*2)) //it has have twice size of shadowmap size pixels = glbuffers.newdirectbytebuffer(shadowmapwidth*shadowmapheight*4);  //set default frame buffer before doing check //http://www.opengl.org/wiki/fbo#completeness_rules gl.glbindframebuffer(gl2.gl_framebuffer, 0);  int status = gl.glcheckframebufferstatus(gl2.gl_framebuffer);  // check our framebuffer ok if(gl.glcheckframebufferstatus(gl2.gl_framebuffer) != gl2.gl_framebuffer_complete) {     system.err.println("can not use fbo! status error:" + status); }  }  public void display(glautodrawable drawable) {     gl2 gl = drawable.getgl().getgl2(); // opengl graphics context     gl.glclear(gl2.gl_color_buffer_bit | gl2.gl_depth_buffer_bit);       gl.glloadidentity();  // reset model-view matrix      //render scene frame buffer first     gl.glbindframebuffer(gl2.gl_framebuffer, framebufferid[0]);         rendersmallscene(gl);      //read pixels buffer     gl.glbindframebuffer(gl2.gl_read_framebuffer, framebufferid[0]);     //read pixels      gl.glreadpixels(0, 0, shadowmapwidth, shadowmapheight, gl2.gl_depth_component , gl2.gl_unsigned_byte, pixels);      //switch default fbo     gl.glbindframebuffer(gl2.gl_framebuffer, 0);         drawsceneobjects(gl);       //draw pixels, format has have 1      gl.gldrawpixels(shadowmapwidth, shadowmapheight, gl2.gl_luminance , gl2.gl_unsigned_byte, pixels);     } 

working result:

you must read using fbo , opengl in general.

in code create fbo , attachments in each frame. that's wrong.it's huge overhead.construct fbos on init once.second, must bind fbo in order draw (or read it), otherwise opengl draw default fbo.take here , here

so ,once fbo ready render this:

glbindframebuffer((gl_draw_framebuffer, yourfbo);     drawsceneobjects(gl);  glbindframebuffer((gl_read_framebuffer, yourfbo);     readpixelshere()    glbindframebuffer((gl_framebuffer, 0);///switch default fbo 

in fact , in case ,as leave fbo bound,just call

    glbindframebuffer((gl_read_framebuffer, yourfbo); 

after drawing geometry.

also , if not using shaders there no reason use textures fbo attachments.create render buffer instead.