Billboarding Problem

Graphics and GPU Programming Programming

Started by Lithic February 08, 2004 09:18 PM

2 comments, last by Lithic 20 years, 2 months ago

345

Author

February 08, 2004 09:18 PM

I''ve just put the finishing touches on my sky and but one small problem remains. I''ve looked at several billboarding posts and implemented a billboard for my sun. However, when rendered, the sun does ugly things when the view direction changes. How can I correct this, code is below:


		float matrix[16];
		glGetFloatv(GL_MODELVIEW_MATRIX, (GLfloat *)matrix); // get modelview matrix
		glEnable(GL_TEXTURE_2D);
		glBindTexture(GL_TEXTURE_2D, texture[4]);			// Set sun texture
		sunCoord[0] *= 5.0f; // multiply sun position to make it further away
		sunCoord[1] *= 5.0f;
		sunCoord[2] *= 5.0f;
		glBegin(GL_QUADS);        // Draw sun
			glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
			glTexCoord2f(0.0f, 0.0f);
			glVertex3f(sunCoord[0] - matrix[0] - matrix[4], sunCoord[1] - matrix[1] - matrix[5], sunCoord[2] - matrix[2] - matrix[6]);
			glTexCoord2f(1.0f, 0.0f);
			glVertex3f(sunCoord[0] + matrix[0] - matrix[4], sunCoord[1] + matrix[1] - matrix[5], sunCoord[2] + matrix[2] - matrix[6]);
			glTexCoord2f(1.0f, 1.0f);
			glVertex3f(sunCoord[0] + matrix[0] + matrix[4], sunCoord[1] + matrix[1] + matrix[5], sunCoord[2] + matrix[2] + matrix[6]);
			glTexCoord2f(0.0f, 1.0f);
			glVertex3f(sunCoord[0] - matrix[0] + matrix[4], sunCoord[1] - matrix[1] + matrix[5], sunCoord[2] - matrix[2] + matrix[6]);
		glEnd();

pasman

441

February 09, 2004 05:38 PM

Try this...

glBegin(GL_QUADS); // Draw sunglColor4f(1.0f, 1.0f, 1.0f, 1.0f);glTexCoord2f(0.0f, 0.0f);glVertex3f(sunCoord[0] - matrix[0] - matrix[1], sunCoord[1] - matrix[4] - matrix[5], sunCoord[2] - matrix[8] - matrix[9]);glTexCoord2f(1.0f, 0.0f);glVertex3f(sunCoord[0] + matrix[0] - matrix[1], sunCoord[1] + matrix[4] - matrix[5], sunCoord[2] + matrix[8] - matrix[9]);glTexCoord2f(1.0f, 1.0f);glVertex3f(sunCoord[0] + matrix[0] + matrix[1], sunCoord[1] + matrix[4] + matrix[5], sunCoord[2] + matrix[8] + matrix[9]);glTexCoord2f(0.0f, 1.0f);glVertex3f(sunCoord[0] - matrix[0] + matrix[1], sunCoord[1] - matrix[4] + matrix[5], sunCoord[2] - matrix[8] + matrix[9]);glEnd();

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