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OpenGL Problem with Shadows / GLSL shaders

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I have been stuck in GLSL shaders for a couple of weeks now, and I just don't get it workin (though I think I'm close to it). I am using Irrlicht as graphics engine, and I try to get some "sunlight" shadows done, for the moment just with the sun right above the scene, so I created a material that renders the depth of the scene to a texture using an orthogonal camera. The position of this camera is 500 units above the center of the visible scene.

Here are 2 images of the problem I have:


The camera position of the second image is the same as in the first, it's just pitched a little up. I put the whole shading thing online:

I don't think that it's a big problem, I just can't get my mind around it. I've been trying to fix the problem for some weeks now, and I think I'm running in circles, so I though I'd post it here. I hope someone can push me into a direction that helps. Thanks in advance.

Here is the vertex shader for the shadowmap:

struct VS_OUTPUT
vec4 Position;
vec4 Color;

uniform mat4 mWorldViewProj;

VS_OUTPUT vertexMain( in vec3 Position )
vec4 hpos;

hpos = (mWorldViewProj * vec4( Position.x , Position.y , Position.z , 1.00000) );
OUT.Color = hpos;
OUT.Position = hpos;
return OUT;

void main()
VS_OUTPUT xlat_retVal;

xlat_retVal = vertexMain( vec3(gl_Vertex));

gl_Position = vec4( xlat_retVal.Position);
gl_TexCoord[0] = vec4( xlat_retVal.Color);

... and the corresponding fragment shader:

uniform float MaxD;

vec4 packFloatToVec4i(const float value)
const vec4 bitSh = vec4(256.0*256.0*256.0, 256.0*256.0, 256.0, 1.0);
const vec4 bitMsk = vec4(0.0, 1.0/256.0, 1.0/256.0, 1.0/256.0);
vec4 res = fract(value * bitSh);
res -= res.xxyz * bitMsk;
return res;

void main()
float depth=((gl_FragCoord.z/gl_FragCoord.w)/MaxD);
gl_FragColor = packFloatToVec4i(depth);

I draw the shadow map on the upper left side of the output window, and (for me) it looks reasonable. Here are the shaders that use the shadowmap:

Vertex shader:

uniform mat4 mWorldViewProj;
uniform mat4 mWorldViewProj2;
uniform mat4 mInvWorld;
uniform float MaxD;

varying vec3 normalVec;
varying vec2 texCoords;
varying float shadowDist;

void main(void)
gl_Position=mWorldViewProj * gl_Vertex;

vec4 shadowPos=mWorldViewProj2*gl_Vertex;

vec4 normal=vec4(gl_Normal, 0.0);
normal=mInvWorld * normal;



vec4 vecDummy=mWorldViewProj2*gl_Vertex;

Fragment Shader:

uniform sampler2D ColoredTextureSampler;

uniform sampler2D ShadowMapSampler;
uniform sampler2D myTexture;
uniform float fShadowMapSize;

varying vec3 normalVec;
varying vec2 texCoords;

varying float shadowDist;

float unpackFloatFromVec4i(const vec4 value)
const vec4 bitSh = vec4(1.0/(256.0*256.0*256.0), 1.0/(256.0*256.0), 1.0/256.0, 1.0);
return(dot(value, bitSh));

float testShadow(vec2 smTexCoord, float realDistance) {
float extractedDistance = unpackFloatFromVec4i(texture2D( ShadowMapSampler, vec2( smTexCoord )));
return (extractedDistance <= realDistance) ? ( 0.5 ) : ( 0.000000 );

void main (void) {
vec4 texColor=texture2D(myTexture,vec2(gl_TexCoord[0]));

if (texColor.a<0.5) discard;

vec3 lightVector=vec3(1,1,0);
vec4 fogColor=vec4(0.227,0.204,0.0,1.0);

float fShadow=0.0;
for (int i=0; i<16; i++) fShadow+=testShadow(texCoords,shadowDist);


and, last but not least, the main .cpp file:

#include <irrlicht.h>
#include <CRoadMeshLoader.h>
#include <CRandomForestNode.h>

using namespace irr;

class CShadowMapper : public video::IShaderConstantSetCallBack {
enum ERenderPass {

IrrlichtDevice *m_pDevice;
scene::ISceneManager *m_pSmgr;
video::ITexture *m_pTexture;
video::IVideoDriver *m_pDrv;
scene::ISceneNode *m_pRoot;
scene::ICameraSceneNode *m_pLightCam;

f32 m_fHeight,
s32 m_iDepthMaterial,
u32 m_iShadowMapSize;

core::array<video::E_MATERIAL_TYPE> m_aMaterials;

core::dimension2du m_cShadowMapDim;

core::matrix4 m_cWorldViewProj,
core::matrix4 m_cInvWorld;
ERenderPass m_iRenderPass;

bool isCulled(scene::ISceneNode *pNode) {
if (pNode->getType()==scene::ESNT_EMPTY) return false;
core::aabbox3d<f32> tbox=pNode->getBoundingBox();
return !(tbox.intersectsWithBox(m_pLightCam->getViewFrustum()->getBoundingBox()));

void render(scene::ISceneNode *pNode) {
if (pNode->getType()==scene::ESNT_TERRAIN) return;

if (pNode->getID()!=-23 && (!isCulled(pNode) || pNode->getType()==scene::ESNT_EMPTY)) {
for (u32 i=0; i<pNode->getMaterialCount(); i++) {
for (u32 i=0; i<pNode->getMaterialCount(); i++) pNode->getMaterial(i).MaterialType=m_aMaterials;
else return;

core::list<scene::ISceneNode *> lChildren=pNode->getChildren();
core::list<scene::ISceneNode *>::Iterator it;

for (it=lChildren.begin(); it!=lChildren.end(); it++) render(*it);

u32 getMaxNumberOfMeshBuffers(scene::ISceneNode *pNode) {
u32 iRet=pNode->getMaterialCount();

for (u32 i=0; i<iRet; i++) {

core::list<scene::ISceneNode *> lChildren=pNode->getChildren();
core::list<scene::ISceneNode *>::Iterator it;

for (it=lChildren.begin(); it!=lChildren.end(); it++) {
u32 i=getMaxNumberOfMeshBuffers(*it);
if (i>iRet) iRet=i;

return iRet;

CShadowMapper(IrrlichtDevice *pDevice, u32 iShadowMapSize, f32 fHeight, scene::ISceneNode *pRoot=NULL) {
//Get the standard Irrlicht instances
m_pSmgr =pDevice->getSceneManager();
m_pDrv =pDevice->getVideoDriver();
m_pRoot =pRoot==NULL?m_pSmgr->getRootSceneNode():pRoot;

//calculate the view frustrum of the current camera
const scene::SViewFrustum *cFrustrum=m_pSmgr->getActiveCamera()->getViewFrustum();
core::vector3df vLeftUp=cFrustrum->getFarLeftUp(),

//initialize some members

//Initialize the Lightcam
core::matrix4 cProjMat;
f32 size=vLeftUp.X; if (size<0.0f) size=-size;

//Compile the shaders
video::IGPUProgrammingServices *pGpu=m_pDrv->getGPUProgrammingServices();

printf("**** compiling pass 1 shaders (fHeight=%.2f)...\n",fHeight);

printf("**** compiling pass 2 shaders...\n");
printf("**** Ready.\n");

u32 iNumberOfTextures=getMaxNumberOfMeshBuffers(m_pRoot);
for (u32 i=0; i<iNumberOfTextures; i++) m_aMaterials.push_back(video::EMT_SOLID);

void update() {
//Activate Lightcam
scene::ICameraSceneNode *pActiveCamera=m_pSmgr->getActiveCamera();

//Calculate new position and target of the lightcam
core::vector3df vPos=pActiveCamera->getPosition(),

if (vPos.Y<0.0f) vPos.Y=0.0f;

//Render the shadowmap

core::recti cRect=core::recti(0,0,m_cShadowMapDim.Width,m_cShadowMapDim.Height);

m_pDrv->setTransform(video::ETS_VIEW ,m_pLightCam->getViewMatrix ());

//restore the active camera

virtual void OnSetConstants(video::IMaterialRendererServices* services, s32 userData) {
switch (m_iRenderPass) {
case enPassShadow:
m_cWorldViewProj =m_pDrv->getTransform(video::ETS_PROJECTION);

services->setVertexShaderConstant("mWorldViewProj",m_cWorldViewProj.pointer(), 16);


case enPassFinal: {

services->setVertexShaderConstant("mInvWorld", m_cInvWorld.pointer(), 16);

m_cWorldViewProj =m_pDrv->getTransform(video::ETS_PROJECTION);

services->setVertexShaderConstant("mWorldViewProj", m_cWorldViewProj.pointer(), 16);

core::matrix4 dummy=m_pLightCam->getViewMatrix();

m_cWorldViewProj2 =m_pLightCam->getProjectionMatrix();
m_cWorldViewProj2*=m_pDrv ->getTransform(video::ETS_WORLD);
services->setVertexShaderConstant("mWorldViewProj2", m_cWorldViewProj2.pointer(), 16);

core::matrix4 world = m_pDrv->getTransform(video::ETS_WORLD);
world = world.getTransposed();

services->setVertexShaderConstant("mTransWorld",world.pointer(), 16);

s32 var0=0;
services->setPixelShaderConstant("ColoredTextureSampler", (f32 *)(&var0), 1);


f32 MaxD=m_fHeight;

s32 var2=1;
services->setPixelShaderConstant("ShadowMapSampler",(f32 *)&var2,1);

video::ITexture *getDepthMap() { return m_pTexture; }

int main() {
core::dimension2du cWindowSize=core::dimension2du(1280,1024);

IrrlichtDevice *pDevice=createDevice(video::EDT_OPENGL,cWindowSize,32,false,false,false,0);

pDevice->setWindowCaption(L"Hello World! - Irrlicht Engine Demo");

video::IVideoDriver *pDrv =pDevice->getVideoDriver();
scene::ISceneManager *pSmgr =pDevice->getSceneManager();
gui::IGUIEnvironment *pGuienv=pDevice->getGUIEnvironment();

CRandomForestFactory *pForest=new CRandomForestFactory(pSmgr);

CRoadMeshLoader *pRoad=new CRoadMeshLoader(pDevice);


scene::ICameraSceneNode *pFpsCam=pSmgr->addCameraSceneNodeFPS();


u32 iShadowSize=2048;

CShadowMapper *pShadow=new CShadowMapper(pDevice,iShadowSize,500.0f,pSmgr->getSceneNodeFromName("worldNode"));
video::ITexture *pDepth=pShadow->getDepthMap();

s32 iLastFPS=-1;
while(pDevice->run()) {



s32 iFps=pDrv->getFPS();

if (iLastFPS!=iFps) {
core::stringw str = L"Shadow Mapping [";
str+="] FPS:";



return 0;

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No idea what I'm looking at. I see a shadow in the first image (what is wrong with it). The second image you don't show the ground so I can't see what is wrong.

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I'm thinking the issue is that blue checkered rectangle. If the 'sun' position is directly above the scene then the whole thing should be in shadow, not just the bottom quarter. Then in the second image the view angle is higher, but the exact same shadow is now farther up the rectangle. My assumption is you're using the wrong coordinates for your shadow calculation so it's taking the 'cameras' movement/view into account, as can happen with lighting.

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      creates a special rotation-translation matrix that moves and rotates the grid away from the origin so that when i finally
      normalize all the vertices on my vertex shader i can get a perfect sphere.
      T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, 1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(180.0), glm::dvec3(1.0, 0.0, 0.0)); sides[0] = new TerrainNode(1.0, radius, T * R, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_FRONT)); T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, -1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(0.0), glm::dvec3(1.0, 0.0, 0.0)); sides[1] = new TerrainNode(1.0, radius, R * T, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_BACK)); // So on and so forth for the rest of the sides As you can see, for the front side grid, i rotate it 180 degrees to make it face the camera and push it towards the eye;
      the back side is handled almost the same way only that i don't need to rotate it but simply push it away from the eye.
      The same technique is applied for the rest of the faces (obviously, with the proper rotations / translations).
      The matrix that result from the multiplication of R and T (in that particular order) is send to my vertex shader as `r_Grid'.
      // spherify vec3 V = normalize((r_Grid * vec4(r_Vertex, 1.0)).xyz); gl_Position = r_ModelViewProjection * vec4(V, 1.0); The `r_ModelViewProjection' matrix is generated on the CPU in this manner.
      // No the most efficient way, but it works. glm::dmat4 Camera::getMatrix() { // Create the view matrix // Roll, Yaw and Pitch are all quaternions. glm::dmat4 View = glm::toMat4(Roll) * glm::toMat4(Pitch) * glm::toMat4(Yaw); // The model matrix is generated by translating in the oposite direction of the camera. glm::dmat4 Model = glm::translate(glm::dmat4(1.0), -Position); // Projection = glm::perspective(fovY, aspect, zNear, zFar); // zNear = 0.1, zFar = 1.0995116e12 return Projection * View * Model; } I managed to get rid of z-fighting by using a technique called Logarithmic Depth Buffer described in this article; it works amazingly well, no z-fighting at all, at least not visible.
      Each frame i'm rendering each node by sending the generated matrices this way.
      // set the r_ModelViewProjection uniform // Sneak in the mRadiusMatrix which is a matrix that contains the radius of my planet. Shader::setUniform(0, Camera::getInstance()->getMatrix() * mRadiusMatrix); // set the r_Grid matrix uniform i created earlier. Shader::setUniform(1, r_Grid); grid->render(); My planet's radius is around 6400000.0 units, absurdly large, but that's what i really want to achieve;
      Everything works well, the node's split and merge as you'd expect, however whenever i get close to the surface
      of the planet the rounding errors start to kick in giving me that lovely stairs effect.
      I've read that if i could render each grid relative to the camera i could get better precision on the surface, effectively
      getting rid of those rounding errors.
      My question is how can i achieve this relative to camera rendering in my scenario here?
      I know that i have to do most of the work on the CPU with double, and that's exactly what i'm doing.
      I only use double on the CPU side where i also do most of the matrix multiplications.
      As you can see from my vertex shader i only do the usual r_ModelViewProjection * (some vertex coords).
      Thank you for your suggestions!
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