question: void renderShadowMap ( ) { glUseProgram ( shadowProgram ) ; glUniformMatrix4fv ( shadowProgramVPUniform , false , light . get ( matrixBuffer ) ) ; glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT , fbo ) ; glViewport ( 0 , 0 , shadowMapSize , shadowMapSize ) ; glClear ( GL_DEPTH_BUFFER_BIT ) ; glDrawArrays ( GL_TRIANGLES , 0 , 6 * 6 * boxes . length ) ; glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT , 0 ) ; glUseProgram ( 0 ) ; }
target:  Render the shadow map into a depth texture.