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maxfire

OpenGL
Opengl Texture lightingissue

3 posts in this topic

Hi gys I am fairly new to Opengl and am currently having some issues with lighting on a texture. Basically I am trying to create a simple lighting demo that consists of a spinning block with lighting. Now I have my spinning block coloured white and its rotating on the y axis no problems there. Simple stuff so far. Following on from added some simple lighting ( ambient, positioned and directed ), worked like a charm. I have my spinning white block with some nice lighting. Now here is where I hit the wall, after loading a texture, binding it and setting its coordinates the texture displays but its unaffected by lighting. Now I have scowered the internet looking for a solution, the openGL documentations tells me I need to add
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); ( if my understanding of this is correct it tells textures to be processed per vertex rather then over the spread of the texture) so I added this line of code sadly it made no difference. Now I have backtracked through some tutorial I originally read to double check my code. I believe all my declarations are correct so I think I might be doing something in the wrong order??

heres some code of my code

startup function
[CODE]
bool MainWnd::InitGL()
{
//Set clear color
//glClearColor( 0, 0, 0, 0 );
glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
//Set projection
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluPerspective( 45.0, (double)Initialize::SCREEN_WIDTH / (double)Initialize::SCREEN_HEIGHT, 1.0, 200.0 );
glViewport( 0, 0, Initialize::SCREEN_WIDTH, Initialize::SCREEN_HEIGHT );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
glEnable( GL_BLEND );
glBlendFunc( GL_ONE, GL_ONE_MINUS_SRC_ALPHA );
//lighting and shading
glEnable( GL_LIGHTING );
glEnable( GL_LIGHT0 );
glEnable( GL_LIGHT1 );
glShadeModel( GL_SMOOTH );
glEnable( GL_COLOR_MATERIAL );
glEnable( GL_DEPTH_TEST );
glEnable( GL_NORMALIZE );
//Initialize modelview matrix
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();

//If there was any errors
if( glGetError() != GL_NO_ERROR )
{
ErrorSystem::instance().WriteError( "MainWnd GL load Fail" );
return false;
}
//If everything initialized
return true;
}
[/CODE]

Lighting setup
[CODE]
void LogicEngine::DoDrawing()
{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glLoadIdentity();
_Camera->Render();

//Add ambient light
GLfloat ambientColor[] = {1.0f, 1.0f, 1.0f, 1.0f}; //Color (0.2, 0.2, 0.2)
glLightModelfv( GL_LIGHT_MODEL_AMBIENT, ambientColor );

//Add positioned light
GLfloat lightColor0[] = {0.5f, 0.5f, 0.5f, 0.0f};
GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 1.0f};
glLightfv( GL_LIGHT0, GL_DIFFUSE, lightColor0 );
glLightfv( GL_LIGHT0, GL_POSITION, lightPos0 );

//Add directed light
GLfloat lightColor1[] = {0.5f, 0.2f, 0.2f, 10.0f};
GLfloat lightPos1[] = {-1.0f, 0.5f, 0.5f, 1.0f};
glLightfv( GL_LIGHT1, GL_DIFFUSE, lightColor1 );
glLightfv( GL_LIGHT1, GL_POSITION, lightPos1 );

DrawBoxes();
//DrawTerrain();
SDL_GL_SwapBuffers();
}
[/CODE]

DrawBox
[CODE]
void LogicEngine::DrawBoxes()
{
glPushMatrix();
glTranslatef(0.0f, 1.5f, -8.0f);
glRotatef(_Angle, 0.0f, 1.0f, 0.0f);
glColor4ub( 255,255,255,255 );

glEnable( GL_TEXTURE_2D );
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );
glBindTexture(GL_TEXTURE_2D, _pFace1->GetTexture());
float x = 0;
float y = 0;
glBegin(GL_QUADS);
//Front

x = GetClippingPercentage( 0, _pFace1->_TextureDimentions.width );
y = GetClippingPercentage( 0, _pFace1->_TextureDimentions.height );

//TL
glNormal3f(-1.0f, 0.0f, 1.0f);
glTexCoord2f( x, y );
glVertex3f(-1.5f, -1.0f, 1.5f);
x = GetClippingPercentage( _pFace1->_SpriteDimentions.width, _pFace1->_TextureDimentions.width );
y = GetClippingPercentage( 0, _pFace1->_TextureDimentions.height );
//TR
glNormal3f(1.0f, 0.0f, 1.0f);
glTexCoord2f( x, y );
glVertex3f(1.5f, -1.0f, 1.5f);
x = GetClippingPercentage( _pFace1->_SpriteDimentions.width, _pFace1->_TextureDimentions.width );
y = GetClippingPercentage( _pFace1->_SpriteDimentions.height, _pFace1->_TextureDimentions.height );
//BR
glNormal3f(1.0f, 0.0f, 1.0f);
glTexCoord2f( x, y );
glVertex3f(1.5f, 1.0f, 1.5f);
x = GetClippingPercentage( 0, _pFace1->_TextureDimentions.width );
y = GetClippingPercentage( _pFace1->_SpriteDimentions.height, _pFace1->_TextureDimentions.height );
//BL
glNormal3f(-1.0f, 0.0f, 1.0f);
glTexCoord2f( x, y );
glVertex3f(-1.5f, 1.0f, 1.5f);

glEnd();

//removed code for second box

glPopMatrix();
}
[/CODE]

Here an image of the output

[img]http://i1265.photobucket.com/albums/jj508/maxfire1/lighterror.png[/img]

Thanks in advanced
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Please notice that you are using legacy OpenGL. If the only purpose is to do the demo, then it is fine. But if you want to learn how to use OpenGL in modern applications, then you will have to discard most of the work.

Lighting is easier to handle when you define the shaders on your own, although the work needed to get something first time up and running is a little bigger. See [url="https://github.com/progschj/OpenGL-Examples"]https://github.com/p...OpenGL-Examples[/url] for some (to begin) simple reference implementations.

See also [url="http://www.arcsynthesis.org/gltut/"]http://www.arcsynthesis.org/gltut/[/url] for a nice tutorial. Edited by larspensjo
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thanks for the info dude, I actually have found the problem. It was the fact that I was setting my ambient lighting to perfect white so in fact my other lighting sources were working fine it just wasn't showing through because the ambient lighting was over power it

if you wouldn't mind can you point me in the direction of some new "up to date" lighting references/tutorials :)
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[quote name='MaxFire' timestamp='1341691170' post='4956723']
if you wouldn't mind can you point me in the direction of some new "up to date" lighting references/tutorials
[/quote]
Actually, lighting is not really part of OpenGL, there are no such things as lights anymore. Instead, you define the fragment shader program that computes the color of each fragment (pixel). If you want lighting, you add some color. It may look like hard work, and the initial step takes some work. But looking at good tutorials and copying other examples helps you to get going. The tutorial reference I showed above is very good on that regard. It is not only about OpenGL, it is about the modern way to do 3D with OpenGL. More specifically, see [url="http://www.arcsynthesis.org/gltut/Illumination/Tutorial%2009.html#d0e8853"]http://www.arcsynthesis.org/gltut/Illumination/Tutorial%2009.html#d0e8853[/url]. But don't skip the initial part of the tutorial too quickly.
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