scummvm/graphics/tinygl/vertex.cpp

#include "graphics/tinygl/zgl.h"

#include <string.h>

void glopNormal(GLContext *c, TGLParam *p) {
	V3 v;

	v.X = p[1].f;
	v.Y = p[2].f;
	v.Z = p[3].f;

	c->current_normal.X = v.X;
	c->current_normal.Y = v.Y;
	c->current_normal.Z = v.Z;
	c->current_normal.W = 0;
}

void glopTexCoord(GLContext *c, TGLParam *p) {
	c->current_tex_coord.X = p[1].f;
	c->current_tex_coord.Y = p[2].f;
	c->current_tex_coord.Z = p[3].f;
	c->current_tex_coord.W = p[4].f;
}

void glopEdgeFlag(GLContext *c, TGLParam *p) {
	c->current_edge_flag = p[1].i;
}

void glopColor(GLContext *c, TGLParam *p){
	c->current_color.X = p[1].f;
	c->current_color.Y = p[2].f;
	c->current_color.Z = p[3].f;
	c->current_color.W = p[4].f;
	c->longcurrent_color[0] = p[5].ui;
	c->longcurrent_color[1] = p[6].ui;
	c->longcurrent_color[2] = p[7].ui;

	if (c->color_material_enabled) {
		TGLParam q[7];
		q[0].op = OP_Material;
		q[1].i = c->current_color_material_mode;
		q[2].i = c->current_color_material_type;
		q[3].f = p[1].f;
		q[4].f = p[2].f;
		q[5].f = p[3].f;
		q[6].f = p[4].f;
		glopMaterial(c, q);
	}
}

void gl_eval_viewport(GLContext *c) {
	GLViewport *v;
	float zsize = (1 << (ZB_Z_BITS + ZB_POINT_Z_FRAC_BITS));

	v = &c->viewport;

	v->trans.X = (float)(((v->xsize - 0.5) / 2.0) + v->xmin);
	v->trans.Y = (float)(((v->ysize - 0.5) / 2.0) + v->ymin);
	v->trans.Z = (float)(((zsize - 0.5) / 2.0) + ((1 << ZB_POINT_Z_FRAC_BITS)) / 2);

	v->scale.X = (float)((v->xsize - 0.5) / 2.0);
	v->scale.Y = (float)(-(v->ysize - 0.5) / 2.0);
	v->scale.Z = (float)(-((zsize - 0.5) / 2.0));
}

void glopBegin(GLContext *c, TGLParam *p) {
	int type;
	M4 tmp;

	assert(c->in_begin == 0);

	type = p[1].i;
	c->begin_type = type;
	c->in_begin = 1;
	c->vertex_n = 0;
	c->vertex_cnt = 0;

	if (c->matrix_model_projection_updated) {
		if (c->lighting_enabled) {
			// precompute inverse modelview
			gl_M4_Inv(&tmp, c->matrix_stack_ptr[0]);
			gl_M4_Transpose(&c->matrix_model_view_inv, &tmp);
		} else {
			float *m = &c->matrix_model_projection.m[0][0];
			// precompute projection matrix
			gl_M4_Mul(&c->matrix_model_projection,
					c->matrix_stack_ptr[1],
					c->matrix_stack_ptr[0]);
			// test to accelerate computation
			c->matrix_model_projection_no_w_transform = 0;
			if (m[12] == 0.0 && m[13] == 0.0 && m[14] == 0.0)
				c->matrix_model_projection_no_w_transform = 1;
		}

		// test if the texture matrix is not Identity
		c->apply_texture_matrix = !gl_M4_IsId(c->matrix_stack_ptr[2]);

		c->matrix_model_projection_updated = 0;
	}
	// viewport
	if (c->viewport.updated) {
		gl_eval_viewport(c);
		c->viewport.updated = 0;
	}
    // triangle drawing functions
	if (c->render_mode == TGL_SELECT) {
		c->draw_triangle_front = gl_draw_triangle_select;
		c->draw_triangle_back = gl_draw_triangle_select;
	} else {
		switch (c->polygon_mode_front) {
		case TGL_POINT:
			c->draw_triangle_front = gl_draw_triangle_point;
			break;
		case TGL_LINE:
			c->draw_triangle_front = gl_draw_triangle_line;
			break;
		default:
			c->draw_triangle_front = gl_draw_triangle_fill;
			break;
		}

		switch (c->polygon_mode_back) {
		case TGL_POINT:
			c->draw_triangle_back = gl_draw_triangle_point;
			break;
		case TGL_LINE:
			c->draw_triangle_back = gl_draw_triangle_line;
			break;
		default:
			c->draw_triangle_back = gl_draw_triangle_fill;
			break;
		}
	}
}

// coords, tranformation, clip code and projection
// TODO : handle all cases
static inline void gl_vertex_transform(GLContext *c, GLVertex *v) {
	float *m;
	V4 *n;

	if (c->lighting_enabled) {
		// eye coordinates needed for lighting 

		m = &c->matrix_stack_ptr[0]->m[0][0];
		v->ec.X = (v->coord.X * m[0] + v->coord.Y * m[1] +
				v->coord.Z * m[2] + m[3]);
		v->ec.Y = (v->coord.X * m[4] + v->coord.Y * m[5] +
				v->coord.Z * m[6] + m[7]);
		v->ec.Z = (v->coord.X * m[8] + v->coord.Y * m[9] +
				v->coord.Z * m[10] + m[11]);
		v->ec.W = (v->coord.X * m[12] + v->coord.Y * m[13] +
				v->coord.Z * m[14] + m[15]);

		// projection coordinates
		m = &c->matrix_stack_ptr[1]->m[0][0];
		v->pc.X = (v->ec.X * m[0] + v->ec.Y * m[1] + v->ec.Z * m[2] + v->ec.W * m[3]);
		v->pc.Y = (v->ec.X * m[4] + v->ec.Y * m[5] + v->ec.Z * m[6] + v->ec.W * m[7]);
		v->pc.Z = (v->ec.X * m[8] + v->ec.Y * m[9] + v->ec.Z * m[10] + v->ec.W * m[11]);
		v->pc.W = (v->ec.X * m[12] + v->ec.Y * m[13] + v->ec.Z * m[14] + v->ec.W * m[15]);

		m = &c->matrix_model_view_inv.m[0][0];
		n = &c->current_normal;

		v->normal.X = (n->X * m[0] + n->Y * m[1] + n->Z * m[2]);
		v->normal.Y = (n->X * m[4] + n->Y * m[5] + n->Z * m[6]);
		v->normal.Z = (n->X * m[8] + n->Y * m[9] + n->Z * m[10]);

		if (c->normalize_enabled) {
			gl_V3_Norm(&v->normal);
		}
		} else {
		// no eye coordinates needed, no normal
		// NOTE: W = 1 is assumed
		m = &c->matrix_model_projection.m[0][0];

		v->pc.X = (v->coord.X * m[0] + v->coord.Y * m[1] + v->coord.Z * m[2] + m[3]);
		v->pc.Y = (v->coord.X * m[4] + v->coord.Y * m[5] + v->coord.Z * m[6] + m[7]);
		v->pc.Z = (v->coord.X * m[8] + v->coord.Y * m[9] + v->coord.Z * m[10] + m[11]);
		if (c->matrix_model_projection_no_w_transform) {
			v->pc.W = m[15];
		} else {
			v->pc.W = (v->coord.X * m[12] + v->coord.Y * m[13] + v->coord.Z * m[14] + m[15]);
		}
	}

	v->clip_code = gl_clipcode(v->pc.X, v->pc.Y, v->pc.Z, v->pc.W);
}

void glopVertex(GLContext *c, TGLParam *p) {
	GLVertex *v;
	int n, i, cnt;

	assert(c->in_begin != 0);

	n = c->vertex_n;
	cnt = c->vertex_cnt;
	cnt++;
	c->vertex_cnt = cnt;

	// quick fix to avoid crashes on large polygons
	if (n >= c->vertex_max) {
		GLVertex *newarray;
		c->vertex_max <<= 1;	// just double size
		newarray = (GLVertex *)gl_malloc(sizeof(GLVertex) * c->vertex_max);
		if (!newarray) {
			error("unable to allocate GLVertex array.");
		}
		memcpy(newarray, c->vertex, n * sizeof(GLVertex));
		gl_free(c->vertex);
		c->vertex = newarray;
	}
	// new vertex entry
	v = &c->vertex[n];
	n++;

	v->coord.X = p[1].f;
	v->coord.Y = p[2].f;
	v->coord.Z = p[3].f;
	v->coord.W = p[4].f;

	gl_vertex_transform(c, v);

	// color

	if (c->lighting_enabled) {
		gl_shade_vertex(c, v);
	} else {
		v->color = c->current_color;
	}

	// tex coords

	if (c->texture_2d_enabled) {
		if (c->apply_texture_matrix) {
			gl_M4_MulV4(&v->tex_coord, c->matrix_stack_ptr[2], &c->current_tex_coord);
		} else {
			v->tex_coord = c->current_tex_coord;
		}
	}
    // precompute the mapping to the viewport
	if (v->clip_code == 0)
		gl_transform_to_viewport(c, v);

    // edge flag

	v->edge_flag = c->current_edge_flag;

	switch (c->begin_type) {
	case TGL_POINTS:
		gl_draw_point(c, &c->vertex[0]);
		n = 0;
		break;
	case TGL_LINES:
		if (n == 2) {
			gl_draw_line(c, &c->vertex[0], &c->vertex[1]);
			n = 0;
		}
		break;
    case TGL_LINE_STRIP:
    case TGL_LINE_LOOP:
		if (n == 1) {
			c->vertex[2] = c->vertex[0];
		} else if (n == 2) {
			gl_draw_line(c, &c->vertex[0], &c->vertex[1]);
			c->vertex[0] = c->vertex[1];
			n = 1;
		}
		break;
	case TGL_TRIANGLES:
		if (n == 3) {
			gl_draw_triangle(c, &c->vertex[0], &c->vertex[1], &c->vertex[2]);
			n = 0;
		}
		break;
	case TGL_TRIANGLE_STRIP:
		if (cnt >= 3) {
			if (n == 3)
			n = 0;
			// needed to respect triangle orientation
			switch (cnt & 1) {
			case 0:
      			gl_draw_triangle(c, &c->vertex[2], &c->vertex[1], &c->vertex[0]);
      			break;
			default:
			case 1:
      			gl_draw_triangle(c,&c->vertex[0], &c->vertex[1], &c->vertex[2]);
      			break;
			}
		}
		break;
    case TGL_TRIANGLE_FAN:
		if (n == 3) {
			gl_draw_triangle(c, &c->vertex[0], &c->vertex[1], &c->vertex[2]);
			c->vertex[1] = c->vertex[2];
			n = 2;
		}
		break;
    case TGL_QUADS:
		if (n == 4) {
			c->vertex[2].edge_flag = 0;
			gl_draw_triangle(c, &c->vertex[0], &c->vertex[1], &c->vertex[2]);
			c->vertex[2].edge_flag = 1;
			c->vertex[0].edge_flag = 0;
			gl_draw_triangle(c, &c->vertex[0], &c->vertex[2], &c->vertex[3]);
			n = 0;
		}
		break;
	case TGL_QUAD_STRIP:
		if (n == 4) {
			gl_draw_triangle(c, &c->vertex[0], &c->vertex[1], &c->vertex[2]);
			gl_draw_triangle(c, &c->vertex[1], &c->vertex[3], &c->vertex[2]);
			for (i = 0; i < 2; i++)
				c->vertex[i] = c->vertex[i + 2];
			n = 2;
		}
		break;
	case TGL_POLYGON:
		break;
    default:
		error("glBegin: type %x not handled", c->begin_type);
	}

	c->vertex_n = n;
}

void glopEnd(GLContext *c, TGLParam *) {
	assert(c->in_begin == 1);

	if (c->begin_type == TGL_LINE_LOOP) {
		if (c->vertex_cnt >= 3) {
			gl_draw_line(c, &c->vertex[0], &c->vertex[2]);
		}
	} else if (c->begin_type == TGL_POLYGON) {
		int i = c->vertex_cnt;
		while (i >= 3) {
			i--;
			gl_draw_triangle(c, &c->vertex[i], &c->vertex[0], &c->vertex[i - 1]);
		}
	}
	c->in_begin = 0;
}