scummvm/graphics/tinygl/light.cpp

#include "graphics/tinygl/zgl.h"

namespace TinyGL {

void glopMaterial(GLContext *c, GLParam *p) {
	int mode = p[1].i;
	int type = p[2].i;
	float v[4] = { p[3].f, p[4].f, p[5].f, p[6].f };
	int i;
	GLMaterial *m;

	if (mode == TGL_FRONT_AND_BACK) {
		p[1].i=TGL_FRONT;
		glopMaterial(c,p);
		mode=TGL_BACK;
	}
	if (mode == TGL_FRONT)
		m = &c->materials[0];
	else
		m = &c->materials[1];

	switch (type) {
	case TGL_EMISSION:
		for (i = 0; i < 4; i++)
			m->emission.v[i] = v[i];
		break;
	case TGL_AMBIENT:
		for (i = 0; i < 4; i++)
			m->ambient.v[i] = v[i];
		break;
	case TGL_DIFFUSE:
		for (i = 0; i < 4; i++)
			m->diffuse.v[i] = v[i];
		break;
	case TGL_SPECULAR:
		for (i = 0; i < 4; i++)
			m->specular.v[i] = v[i];
		break;
	case TGL_SHININESS:
		m->shininess = v[0];
		m->shininess_i = (int)(v[0] / 128.0f) * SPECULAR_BUFFER_RESOLUTION;
		break;
	case TGL_AMBIENT_AND_DIFFUSE:
		for (i = 0; i < 4; i++)
			m->diffuse.v[i] = v[i];
		for (i = 0; i < 4; i++)
			m->ambient.v[i] = v[i];
		break;
	default:
		assert(0);
	}
}

void glopColorMaterial(GLContext *c, GLParam *p) {
	int mode = p[1].i;
	int type = p[2].i;

	c->current_color_material_mode = mode;
	c->current_color_material_type = type;
}

void glopLight(GLContext *c, GLParam *p) {
	int light=p[1].i;
	int type=p[2].i;
	V4 v;
	GLLight *l;
	int i;
  
	assert(light >= TGL_LIGHT0 && light < TGL_LIGHT0+T_MAX_LIGHTS );

	l = &c->lights[light - TGL_LIGHT0];

	for (i = 0; i < 4; i++)
		v.v[i] = p[3 + i].f;

	switch(type) {
	case TGL_AMBIENT:
		l->ambient = v;
		break;
	case TGL_DIFFUSE:
		l->diffuse = v;
		break;
	case TGL_SPECULAR:
		l->specular = v;
		break;
	case TGL_POSITION:
		{
			V4 pos;
			gl_M4_MulV4(&pos, c->matrix_stack_ptr[0], &v);

			l->position=pos;

			if (l->position.v[3] == 0) {
				l->norm_position.X = pos.X;
				l->norm_position.Y = pos.Y;
				l->norm_position.Z = pos.Z;

				gl_V3_Norm(&l->norm_position);
			}
		}
		break;
	case TGL_SPOT_DIRECTION:
		for (i = 0; i < 3; i++) {
			l->spot_direction.v[i]=v.v[i];
			l->norm_spot_direction.v[i]=v.v[i];
		}
		gl_V3_Norm(&l->norm_spot_direction);
		break;
	case TGL_SPOT_EXPONENT:
		l->spot_exponent = v.v[0];
		break;
	case TGL_SPOT_CUTOFF:
		{
			float a = v.v[0];
			assert(a == 180 || (a >= 0 && a <= 90));
			l->spot_cutoff=a;
			if (a != 180)
				l->cos_spot_cutoff = (float)(cos(a * LOCAL_PI / 180.0));
		}
		break;
	case TGL_CONSTANT_ATTENUATION:
		l->attenuation[0] = v.v[0];
		break;
	case TGL_LINEAR_ATTENUATION:
		l->attenuation[1] = v.v[0];
		break;
	case TGL_QUADRATIC_ATTENUATION:
		l->attenuation[2] = v.v[0];
		break;
	default:
		assert(0);
	}
}
  
void glopLightModel(GLContext *c, GLParam *p) {
	int pname = p[1].i;
	float v[4] = { p[2].f, p[3].f, p[4].f, p[5].f };
	int i;

	switch (pname) {
	case TGL_LIGHT_MODEL_AMBIENT:
		for (i = 0; i < 4; i++) 
			c->ambient_light_model.v[i] = v[i];
		break;
	case TGL_LIGHT_MODEL_LOCAL_VIEWER:
		c->local_light_model = (int)v[0];
		break;
	case TGL_LIGHT_MODEL_TWO_SIDE:
		c->light_model_two_side = (int)v[0];
		break;
	default:
		warning("glopLightModel: illegal pname: 0x%x", pname);
		break;
	}
}


static inline float clampf(float a, float min, float max) {
  if (a < min)
	  return min;
  else if (a > max)
	  return max;
  else
	  return a;
}

void gl_enable_disable_light(GLContext *c, int light, int v) {
	GLLight *l = &c->lights[light];
	if (v && !l->enabled) {
		l->enabled = 1;
		l->next = c->first_light;
		c->first_light = l;
		l->prev = NULL;
	} else if (!v && l->enabled) {
		l->enabled = 0;
		if (!l->prev)
			c->first_light = l->next;
		else
			l->prev->next=l->next;
		if (l->next)
			l->next->prev=l->prev;
	}
}

// non optimized lightening model
void gl_shade_vertex(GLContext *c, GLVertex *v) {
	float R, G, B, A;
	GLMaterial *m;
	GLLight *l;
	V3 n, s, d;
	float dist, tmp, att, dot, dot_spot, dot_spec;
	int twoside = c->light_model_two_side;

	m = &c->materials[0];

	n.X = v->normal.X;
	n.Y = v->normal.Y;
	n.Z = v->normal.Z;

	R = m->emission.v[0] + m->ambient.v[0] * c->ambient_light_model.v[0];
	G = m->emission.v[1] + m->ambient.v[1] * c->ambient_light_model.v[1];
	B = m->emission.v[2] + m->ambient.v[2] * c->ambient_light_model.v[2];
	A = clampf(m->diffuse.v[3], 0, 1);

	for (l = c->first_light; l != NULL; l = l->next) {
		float lR, lB, lG;
    
		// ambient
		lR = l->ambient.v[0] * m->ambient.v[0];
		lG = l->ambient.v[1] * m->ambient.v[1];
		lB = l->ambient.v[2] * m->ambient.v[2];

		if (l->position.v[3] == 0) {
			// light at infinity
			d.X = l->position.v[0];
			d.Y=l->position.v[1];
			d.Z=l->position.v[2];
			att=1;
		} else {
			// distance attenuation
			d.X = l->position.v[0] - v->ec.v[0];
			d.Y = l->position.v[1] - v->ec.v[1];
			d.Z = l->position.v[2] - v->ec.v[2];
			dist = sqrt(d.X * d.X + d.Y * d.Y + d.Z * d.Z);
			if (dist > 1E-3) {
				tmp = 1 / dist;
				d.X *= tmp;
				d.Y *= tmp;
				d.Z *= tmp;
			}
			att = 1.0f / (l->attenuation[0] + dist * (l->attenuation[1] +
					dist * l->attenuation[2]));
		}
		dot = d.X * n.X + d.Y * n.Y + d.Z * n.Z;
		if (twoside && dot < 0)
			dot = -dot;
		if (dot > 0) {
			// diffuse light
			lR += dot * l->diffuse.v[0] * m->diffuse.v[0];
			lG += dot * l->diffuse.v[1] * m->diffuse.v[1];
			lB += dot * l->diffuse.v[2] * m->diffuse.v[2];

			// spot light
			if (l->spot_cutoff != 180) {
				dot_spot =- (d.X * l->norm_spot_direction.v[0] +
							d.Y * l->norm_spot_direction.v[1] +
							d.Z * l->norm_spot_direction.v[2]);
				if (twoside && dot_spot < 0)
					dot_spot = -dot_spot;
				if (dot_spot < l->cos_spot_cutoff) {
					// no contribution
					continue;
				} else {
					// TODO: optimize
					if (l->spot_exponent > 0) {
						att = att * pow(dot_spot, l->spot_exponent);
					}
				}
			}

			// specular light
      
			if (c->local_light_model) {
				V3 vcoord;
				vcoord.X = v->ec.X;
				vcoord.Y = v->ec.Y;
				vcoord.Z = v->ec.Z;
				gl_V3_Norm(&vcoord);
				s.X = d.X-vcoord.X;
				s.Y = d.Y-vcoord.X;
				s.Z = d.Z-vcoord.X;
			} else {
				s.X = d.X;
				s.Y = d.Y;
				s.Z = (float)(d.Z + 1.0);
			}
			dot_spec = n.X * s.X + n.Y * s.Y + n.Z * s.Z;
			if (twoside && dot_spec < 0)
				dot_spec = -dot_spec;
			if (dot_spec > 0) {
				GLSpecBuf *specbuf;
				int idx;
				tmp = sqrt(s.X * s.X + s.Y * s.Y + s.Z * s.Z);
				if (tmp > 1E-3) {
					dot_spec = dot_spec / tmp;
				}

				// TODO: optimize
				// testing specular buffer code
				// dot_spec= pow(dot_spec,m->shininess)
				specbuf = specbuf_get_buffer(c, m->shininess_i, m->shininess);
				idx = (int)(dot_spec * SPECULAR_BUFFER_SIZE);
				if (idx > SPECULAR_BUFFER_SIZE)
					idx = SPECULAR_BUFFER_SIZE;

				dot_spec = specbuf->buf[idx];
				lR += dot_spec * l->specular.v[0] * m->specular.v[0];
				lG += dot_spec * l->specular.v[1] * m->specular.v[1];
				lB += dot_spec * l->specular.v[2] * m->specular.v[2];
			}
		}

		R += att * lR;
		G += att * lG;
		B += att * lB;
	}

	v->color.v[0] = clampf(R, 0, 1);
	v->color.v[1] = clampf(G, 0, 1);
	v->color.v[2] = clampf(B, 0, 1);
	v->color.v[3] = A;
}

} // end of namespace TinyGL