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jenny_wui

OpenGL Need some suggestion about lighting and shading

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Hello, I have somehow built a model (partial) which looks like a stadium. I have attached the picture for your kind perusal. The field ground has been textured. Now for a particular position, my model looks too much lighted as you can see the far half of the seats look totally white. I am a bit new in modeling lighting. If I don't consider the specular parameter, my model looks dull and seats are not properly outlined. So I added some specular component of light and shininess to the model. But the far half of the model looks too much lighted. I found textured portion is unaffected by lighting. Could any one explain why?
Could any one suggest how can I adjust the lighting parameters so that model does not look too shiny and seats around the field are also properly outlined.

I am using simple OpenGL, no GLSL.

Thanks in advance to all.

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void initGL(){

	static const GLfloat light_model_ambient[] = {1.0f, 1.0f, 1.0f, 1.0f};
	
	glLightModelfv(GL_LIGHT_MODEL_AMBIENT, light_model_ambient);
	 
	glShadeModel(GL_SMOOTH);
	glEnable(GL_DEPTH_TEST);
	

	float diffuse[]  = {1.0f, 1.0f, 1.0f, 1.0f};
	float position[] = {5.0f, 5.0f, 5.0f, 1.0f};
	float specular[] = {1.0f, 1.0f, 1.0f, 1.0f};

	glEnable(GL_LIGHTING);
	glEnable( GL_LIGHT0);
	glLightfv(GL_LIGHT0, GL_DIFFUSE,  diffuse);
	glLightfv(GL_LIGHT0, GL_POSITION, position);
	glLightfv(GL_LIGHT0, GL_SPECULAR, specular);

	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

	float shininess = 5.0f;
	glEnable(GL_COLOR_MATERIAL);
	glMaterialf( GL_FRONT_AND_BACK, GL_SHININESS, shininess);
       glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,  specular);

	pTextureLoader->SetHighQualityTextures(TRUE);
	pTextureLoader->SetMipMapping(TRUE);
	pTextureLoader->SetTextureFilter(txTrilinear);
	pTextureLoader->LoadTextureFromDisk("grass.jpg", &m_MyLogoTexture);

}

void drawSceneGraphics()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);           

	//Render the checked floor.
	glEnable(GL_BLEND);
	glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
	renderAll();
	
	glDisable(GL_BLEND);
}


void renderAll(){
	
	glPushMatrix();

      //Render the middle textured field

	glEnable(GL_TEXTURE_2D);   
	renderField(size);
	glDisable(GL_TEXTURE_2D);
	glPopMatrix();
				
	// Render track 1 (red color)
   
       glPushMatrix();
	renderTexturedTrack_1(size);
	glPopMatrix();

      // Render Track 2 (blue color)

	glPushMatrix();
	renderTexturedTrack_2(size);
       glPopMatrix();

      // Render seats

	glPushMatrix();
	drawModel();			
	glPopMatrix();

	return;
}


Thanks in advance to all.
void glutReshape(int width, int height)
{
	
	static const double kPI = 3.1415926535897932384626433832795;
	static const double kFovY = 45;

	double nearDist, farDist, aspect;
	

	width =  glutGet(GLUT_WINDOW_WIDTH);
	height = glutGet(GLUT_WINDOW_HEIGHT);

	


	if (width && height)
	{
		glViewport(0, 0, width, height);

		// Compute the viewing parameters based on a fixed fov and viewing
		// a canonical box centered at the origin.

		nearDist = 15.0 / tan((kFovY / 2.0) * kPI / 180.0);
		farDist = nearDist + 70.0;
		aspect = (double) width / height;

		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		gluPerspective(kFovY, aspect, 0.1, 140);

		// Place the camera down the Z axis looking at the origin.

		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();            
		
		gluLookAt(0, 25.0, nearDist + 35.0, 0, 0.0, 0, 0, 1, 0.0);
	

	}
}

I have attached some part of my code. Please provide me some suggestions so that I can fix the lighting parameters.

 

Thanks again in advance.

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Your lighting terms don't look right. From a brief skim of your code:

Why is the ambient term at full intensity? It shouldn't be otherwise you have no dynamic range to work with (hence the washed out lighting). Try a lower value like 0.2f.

Your specular shininess is very broad. A low number such as the one you are using will wash out a lot of your model, especially with vertex lighting (which you are using). Try a higher value like 64.0f or 128.0f.

Your specular term is very bright. This may be contributing to your problem so try a lower value like 0.8f.

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Hi, thank you very much for taking time to answer my question. As per your suggestion I have changed the lighting parameters as follows:

The attached picture is for a shininess value of 128.0f. Setting the value at 64.0f does not make much difference in output.

void initGL()
{
	static const GLfloat light_model_ambient[] = {0.2f, 0.2f, 0.2f, 1.0f};
	
	glLightModelfv(GL_LIGHT_MODEL_AMBIENT, light_model_ambient);
	 
	glShadeModel(GL_SMOOTH);
	glEnable(GL_DEPTH_TEST);

	float diffuse[]  = {1.0f, 1.0f, 1.0f, 1.0f};
	float position[] = {5.0f, 5.0f, 5.0f, 1.0f};
	float specular[] = {0.8f, 0.8f, 0.8f, 1.0f};

	glEnable(GL_LIGHTING);
	glEnable( GL_LIGHT0);
	glLightfv(GL_LIGHT0, GL_DIFFUSE,  diffuse);
	glLightfv(GL_LIGHT0, GL_POSITION, position);
	glLightfv(GL_LIGHT0, GL_SPECULAR, specular);

	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

	float shininess = 128.0f;
	glEnable(GL_COLOR_MATERIAL);
	glMaterialf( GL_FRONT_AND_BACK, GL_SHININESS, shininess);
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,  specular);


	pTextureLoader->SetHighQualityTextures(TRUE);
	pTextureLoader->SetMipMapping(TRUE);
	pTextureLoader->SetTextureFilter(txTrilinear);
	pTextureLoader->LoadTextureFromDisk("grass.jpg", &m_MyLogoTexture);

}

 

 

Could you suggest me what is going wrong with my code.

 

Thanks again an advance.

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I have been able to get better output by adding the following:

glEnable(GL_NORMALIZE);

 

Thank you for sharing ideas. But I have one question why textured portion remains unaffected by lighting?

 

Thanks again.

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