I have developed more than 20 mobile apps using OpenGL ES 2.0. However, I am trying to make a renderer to use my apps in OSX so now I am using OpenGL v3.3 with GLSL v130. Yesterday, I ran into a problem that I can't use a texture(RTT) that I drew particles on Off-Screen FBO with GL_LINES 1.0 size (it is the max value in OpenGL 3.3 why??)
When I drew geometry on the Off Screen FBO and used it as a texture on On-screen, I was able to see that and also if I draw small particles on On-screen I can clearly see those but if I try to draw that particle lines and try to use it as a texture on Main screen I can see only a black texture.
I have already checked GL ERRORs and back FBOs' status and GL blending options but I am still struggling to solve it .
Anyone has a idea to solve it ?
Even though I think my code is okay I attached a little code bellow
// AFTER generate and bind FBO, generate RTT
StarTexture fboTex;
fboTex.texture_width = texture_width;
fboTex.texture_height = texture_height;
glGenTextures(1, &fboTex.texture_id);
glBindTexture(GL_TEXTURE_2D,fboTex.texture_id);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texture_width, texture_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fboTex.texture_id, 0);
and this is drawing particles on BACK FBO
glUniformMatrix4fv( h_Uniforms[UNIFORMS_PROJECTION], 1, GL_FALSE, g_proxtrans.s);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_PARTICLE]);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Vec3)*ParticleNumTotal*2, &p_particle_lc_xy[0]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_POSITION], 3, GL_FLOAT, 0, 0,0);
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_POSITION]);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_COLOR]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_COLOR], 4, GL_FLOAT, 0, 0,0);
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_COLOR]);
glLineWidth(Thickness); // 1.0 because it is maxium
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, h_VBO[VBO_INDEX_OFF1]);
glDrawElements(GL_LINES, 400, GL_UNSIGNED_INT, 0); // 200 lines
and when I draw that on the main screen
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear( GL_COLOR_BUFFER_BIT);
starfbo->bindingVAO1();
glViewport(0, 0, ogl_Width, ogl_Height);
glUseProgram(h_Shader_Program[Shader_Program_FINAL]);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_TEXCOORD2]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_UV2], 2, GL_FLOAT, 0, 0,0);
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_UV2]);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_SQCOORD2]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_POSITION3], 2, GL_FLOAT, 0, 0,0 );
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_POSITION3]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, h_VBO[VBO_INDEX_ON]);
glDrawElements(GL_TRIANGLES,sizeof(squareIndices)/sizeof(squareIndices[0]), GL_UNSIGNED_INT ,(void*)0);
glUniformMatrix4fv( h_Uniforms[UNIFORMS_PROJECTION], 1, GL_FALSE, g_proxtrans.s);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_PARTICLE]);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Vec3)*ParticleNumTotal*2, &p_particle_lc_xy[0]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_POSITION], 3, GL_FLOAT, 0, 0,0);
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_POSITION]);
glBindBuffer(GL_ARRAY_BUFFER, h_VBO[VBO_COLOR]);
glVertexAttribPointer(h_Attributes[ATTRIBUTES_COLOR], 4, GL_FLOAT, 0, 0,0);
glEnableVertexAttribArray(h_Attributes[ATTRIBUTES_COLOR]);
glLineWidth(Thickness);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, h_VBO[VBO_INDEX_OFF1]);
glDrawElements(GL_LINES, 400, GL_UNSIGNED_INT, 0);
glDrawElements(GL_LINES, 400, GL_UNSIGNED_INT, 0);
GL_UNSIGNED_INT can not be used in OpenGL ES Versus OpenGL. Oddly, it works for IOS but not Android.
The parameter must be GL_UNSIGNED_BYTE or GL_UNSIGNED_SHORT in OpenGL ES.