c++ - texture(...) function always returns 0 -

i have been trying shadow mapping work quite time , still no closer month ago. beginning think may issue gl drivers because haven't been able see side effects such "light acne."

i told start using sampler2dshadow instead of sampler2d , did. however, whenever sample map using texture(...) result 0. why happening?

i have tried entering manual depthcoord values , still 0. result of shadowmap (i.e way has been setup?) or driver issue?

framebuffer setup

framebuffername = 0; glgenframebuffers(1, &framebuffername); glbindframebuffer(gl_framebuffer, framebuffername); glgentextures(1, &depthtexture); glbindtexture(gl_texture_2d, depthtexture); gltexparameteri( gl_texture_2d, gl_texture_min_filter, gl_nearest ); gltexparameteri( gl_texture_2d, gl_texture_mag_filter, gl_nearest ); gltexparameteri( gl_texture_2d, gl_texture_wrap_s, gl_clamp_to_edge ); gltexparameteri( gl_texture_2d, gl_texture_wrap_t, gl_clamp_to_edge ); gltexparameteri(gl_texture_2d, gl_texture_compare_func, gl_lequal); gltexparameteri(gl_texture_2d, gl_texture_compare_mode, gl_compare_ref_to_texture); glteximage2d(gl_texture_2d, 0,gl_depth_component, 512, 512, 0, gl_depth_component, gl_float, 0); glframebuffertexture(gl_framebuffer, gl_depth_attachment, depthtexture, 0); gldrawbuffer(gl_none); glreadbuffer(gl_none); glbindframebuffer(gl_framebuffer, 0); 

fragment shader

uniform sampler2dshadow shadowmap; in vec4 depthcoord; void main(){     //the final color after lighting stored 'finalcolor'     float visibility = 1.0;     if (texture(shadowmap, depthcoord.xyz) == 0.0){         visibility = 0.1;     }     color = vec4(finalcolor.rgb * visibility, 1.0); } 

rendering code

    glm::vec3 lightinvdir = glm::vec3(0,-10,-10);     glm::mat4 depthprojectionmatrix = glm::ortho<float>(-10,10,-10,10,-10,20);     glm::mat4 depthviewmatrix = glm::lookat(lightinvdir, glm::vec3(0,0,0), glm::vec3(0,1,0));     glm::mat4 depthmodelmatrix = glm::mat4(1.0);     glm::mat4 depthmvp = depthprojectionmatrix * depthviewmatrix * depthmodelmatrix;     glm::mat4 biasmatrix(                 0.5, 0.0, 0.0, 0.0,                 0.0, 0.5, 0.0, 0.0,                 0.0, 0.0, 0.5, 0.0,                 0.5, 0.5, 0.5, 1.0     );     glm::mat4 depthbiasmvp = biasmatrix*depthmvp;      /*  shadow */     subshader->useshader();     glviewport(0,0,512,512);     gluniformmatrix4fv(glgetuniformlocation(subshader->getshader(),"depthmvp"), 1, gl_false, &depthmvp[0][0]);     glbindframebuffer(gl_framebuffer, shadows::framebuffer());     renderbuffer(objbuffer);     glbindframebuffer(gl_framebuffer, 0);      /* clear */     glclear(gl_color_buffer_bit | gl_depth_buffer_bit);      /* shader */     objshader->useshader();     glactivetexture(gl_texture0);     glbindtexture(gl_texture_2d, shadows::shadowmap());     gluniform1f(glgetuniformlocation(objshader->getshader(),"shadowmap"),0);      /* render scene */     gluniformmatrix4fv(glgetuniformlocation(objshader->getshader(),"depthbiasmvp"), 1, gl_false, &depthbiasmvp[0][0]);     glviewport(0,0,640,480);     gluniform1f(glgetuniformlocation(objshader->getshader(),"renderingpass"),1.0);     renderbuffer(objbuffer); 

the majority of code has been learned sites such (http://www.opengl-tutorial.org/) modifications based on (http://www.fabiensanglard.net/shadowmapping/index.php) , red book.