Blending not working with lighting on!!
Author
Hello, I've got a silly problem with an application I'm making, when I enable lighting, blending does not work, how can a glEnable/glDisable (GL_LIGHTING) affect blending?? while in blending mode, the only thing worth mentioning is that I use alpha testing for displaying alpha textures, does anybody have an idea what may be wrong?? If you need any more specific information I would be happy to send!!
At a guess, it's because you're using vertex colours to affect the alpha of your textures. When you switch on lighting vertex colours are ignored and material colours are used instead. Personally I think thats annoying, and the easiest way around it is to use GL_COLOR_MATERIAL so that material colours are picked up from vertex colours. Typical usage is something like:
glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
Author
I actually use blending to alpha fade between alpha textures and in the transition phase e.g. I use glColor(1,1,1,alpha1) for lod1 & glColor(1,1,1,alpha2) for lod2 in a GL_MODULATE environment. I don't want to use GL_COLOR_MATERIAL in the application,better change materials..So with lighting on, by changing the material color, the alpha fade would work in this case??
Yep. But because which material attribute you change - there are 4 colour factors and they all technically include the alpha channel =)
If you are using TexEnv stuff, im pretty sure you can still use the vertex colour channel with lighting enabled by using it as a source parameter. Not 100% sure on that though, i havent touched that stuff since fragment shaders were introduced.
If you are using TexEnv stuff, im pretty sure you can still use the vertex colour channel with lighting enabled by using it as a source parameter. Not 100% sure on that though, i havent touched that stuff since fragment shaders were introduced.
Author
I changed the material's alpha & still doesn't work..Any other ideas for what the problem might be?? & thanks for your responses so far!!
Can you post a bit of code?
Where are you calling the glMaterialf, and what are you changing?
Where are you calling the glMaterialf, and what are you changing?
Author
ok, I've kept the most important part & trimmed it a little, here it goes :
(I use premultiplied alpha textures)
/************* Part of display func ***********/
glBlendFunc(GL_ONE,GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
for(i=0;i<(uint)forest_treenum_val;i++)
{
dir = cam - CVert(for_pos[0],for_pos[1],for_pos[2]);
dirnorm = dir;
dirnorm.Normalize();
if(Dot(dirnorm,camnorm)>frcos)
{
dirsqlen = dir.SqLength();
SelectLOD(dirsqlen,forest_lodchange,forest_lodzones,perc,lval);
glPushMatrix();
glTranslatef(for_pos[0],for_pos[1],for_pos[2]);
//lod 1
if((lval[0] < config.lod_levels) && (lval[0] >= 0))
{
alphafades[0] = perc[0];
alphalod = 0;
glCallList(drawLODList[lval[0]]);
}
//lod 2
if((lval[1] < config.lod_levels) && (lval[1] >= 0))
{
alphafades[1] = perc[1];
alphalod = 1;
glCallList(drawLODList[lval[1]]);
}
glPopMatrix();
}
else
{
failed++;
}
}
glDisable(GL_BLEND);
/************** Part of display list *****************/
void drawTreeLOD_setup(int *lod_val)
{
glNewList(drawLODList[*lod_val],GL_COMPILE);
uint i,j,k,start=0,size=0;
glEnable(GL_TEXTURE_2D);
// For every Tree level
for(i=0;i<rep[*lod_val].repreNum;i++)
{
switch((int)rep[*lod_val].levelRepre)
{
case (int)geometry :
// Set texture & materials
glBindTexture(GL_TEXTURE_2D,BarkTex[(*(Tree.node_ID))]);
SetMaterialsAlpha(fdatapool.mat[3*(*(Tree.node_ID))],alphafades[alphalod]);
start = fdatapool.geom_lvl2lod_index[i*MAX_TREE_LVL + rep[*lod_val].geomLevel];
size = fdatapool.geom_lvl2lod_size[i*MAX_TREE_LVL + rep[*lod_val].geomLevel];
break;
case (int)texture :
if(Tree.nodetype == leaf)
{
glBindTexture(GL_TEXTURE_2D,LeafTex);
SetMaterials(fdatapool.mat[3*(fdatapool.matmax-2)]);
}
else
{
glBindTexture(GL_TEXTURE_2D,Releasetex);
SetMaterialsAlpha(fdatapool.mat[3*(fdatapool.matmax-1)],alphafades[alphalod]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP);
}
start = fdatapool.tex_lvl_index;
size = fdatapool.tex_lvl_size;
break;
}
for(j=start;j<(start+size);j++)
{
glBegin(GL_TRIANGLES);
for(k=0;k<fdatapool.indiv_data2_size[j];k++)
{
glNormal3fv((GLfloat *)fdatapool.indiv_data2[j].normals[k]);
glTexCoord2fv((GLfloat *)fdatapool.indiv_data2[j].st[k]);
glVertex3fv((GLfloat *)fdatapool.indiv_data2[j].mesh[k]);
}
glEnd();
}
}
glEndList();
if((*lod_val) == (int)(config.lod_levels - 1))
{
glNewList(drawLODList[config.lod_levels],GL_COMPILE);
glEndList();
}
}
/******************* Materials function ***********************/
void SetMaterialsAlpha(float *mat,float alpha)
{
float tmat[12] = {mat[0],mat[1],mat[2],alpha,
mat[4],mat[5],mat[6],alpha,
mat[8],mat[9],mat[10],alpha};
glMaterialfv(GL_FRONT, GL_AMBIENT, tmat);
glMaterialfv(GL_FRONT, GL_DIFFUSE, &tmat[4]);
glMaterialfv(GL_FRONT, GL_SPECULAR, &tmat[8]);
}
(I use premultiplied alpha textures)
/************* Part of display func ***********/
glBlendFunc(GL_ONE,GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
for(i=0;i<(uint)forest_treenum_val;i++)
{
dir = cam - CVert(for_pos[0],for_pos[1],for_pos[2]);
dirnorm = dir;
dirnorm.Normalize();
if(Dot(dirnorm,camnorm)>frcos)
{
dirsqlen = dir.SqLength();
SelectLOD(dirsqlen,forest_lodchange,forest_lodzones,perc,lval);
glPushMatrix();
glTranslatef(for_pos[0],for_pos[1],for_pos[2]);
//lod 1
if((lval[0] < config.lod_levels) && (lval[0] >= 0))
{
alphafades[0] = perc[0];
alphalod = 0;
glCallList(drawLODList[lval[0]]);
}
//lod 2
if((lval[1] < config.lod_levels) && (lval[1] >= 0))
{
alphafades[1] = perc[1];
alphalod = 1;
glCallList(drawLODList[lval[1]]);
}
glPopMatrix();
}
else
{
failed++;
}
}
glDisable(GL_BLEND);
/************** Part of display list *****************/
void drawTreeLOD_setup(int *lod_val)
{
glNewList(drawLODList[*lod_val],GL_COMPILE);
uint i,j,k,start=0,size=0;
glEnable(GL_TEXTURE_2D);
// For every Tree level
for(i=0;i<rep[*lod_val].repreNum;i++)
{
switch((int)rep[*lod_val].levelRepre)
{
case (int)geometry :
// Set texture & materials
glBindTexture(GL_TEXTURE_2D,BarkTex[(*(Tree.node_ID))]);
SetMaterialsAlpha(fdatapool.mat[3*(*(Tree.node_ID))],alphafades[alphalod]);
start = fdatapool.geom_lvl2lod_index[i*MAX_TREE_LVL + rep[*lod_val].geomLevel];
size = fdatapool.geom_lvl2lod_size[i*MAX_TREE_LVL + rep[*lod_val].geomLevel];
break;
case (int)texture :
if(Tree.nodetype == leaf)
{
glBindTexture(GL_TEXTURE_2D,LeafTex);
SetMaterials(fdatapool.mat[3*(fdatapool.matmax-2)]);
}
else
{
glBindTexture(GL_TEXTURE_2D,Releasetex);
SetMaterialsAlpha(fdatapool.mat[3*(fdatapool.matmax-1)],alphafades[alphalod]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP);
}
start = fdatapool.tex_lvl_index;
size = fdatapool.tex_lvl_size;
break;
}
for(j=start;j<(start+size);j++)
{
glBegin(GL_TRIANGLES);
for(k=0;k<fdatapool.indiv_data2_size[j];k++)
{
glNormal3fv((GLfloat *)fdatapool.indiv_data2[j].normals[k]);
glTexCoord2fv((GLfloat *)fdatapool.indiv_data2[j].st[k]);
glVertex3fv((GLfloat *)fdatapool.indiv_data2[j].mesh[k]);
}
glEnd();
}
}
glEndList();
if((*lod_val) == (int)(config.lod_levels - 1))
{
glNewList(drawLODList[config.lod_levels],GL_COMPILE);
glEndList();
}
}
/******************* Materials function ***********************/
void SetMaterialsAlpha(float *mat,float alpha)
{
float tmat[12] = {mat[0],mat[1],mat[2],alpha,
mat[4],mat[5],mat[6],alpha,
mat[8],mat[9],mat[10],alpha};
glMaterialfv(GL_FRONT, GL_AMBIENT, tmat);
glMaterialfv(GL_FRONT, GL_DIFFUSE, &tmat[4]);
glMaterialfv(GL_FRONT, GL_SPECULAR, &tmat[8]);
}
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