shithub: tinygl

ref: f03aac3fa4e87533f0606b6d28a594504d1b0d1f
dir: /src/clip.c/

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#include "msghandling.h"
#include "zgl.h"
/* fill triangle profile */
/* #define PROFILE */

#define CLIP_XMIN (1 << 0)
#define CLIP_XMAX (1 << 1)
#define CLIP_YMIN (1 << 2)
#define CLIP_YMAX (1 << 3)
#define CLIP_ZMIN (1 << 4)
#define CLIP_ZMAX (1 << 5)

void gl_transform_to_viewport(GLContext* c, GLVertex* v) {
	GLfloat winv;

	/* coordinates */
	winv = 1.0 / v->pc.W;
	v->zp.x = (GLint)(v->pc.X * winv * c->viewport.scale.X + c->viewport.trans.X);
	v->zp.y = (GLint)(v->pc.Y * winv * c->viewport.scale.Y + c->viewport.trans.Y);
	v->zp.z = (GLint)(v->pc.Z * winv * c->viewport.scale.Z + c->viewport.trans.Z);
	/* color */
	v->zp.r = (GLuint)(v->color.v[0] * 65535) & 65535;
	v->zp.g = (GLuint)(v->color.v[1] * 65535) & 65535;
	v->zp.b = (GLuint)(v->color.v[2] * 65535) & 65535;

	/* texture */

	if (c->texture_2d_enabled) {
		v->zp.s = (GLint)(v->tex_coord.X * (ZB_POINT_S_MAX - ZB_POINT_S_MIN) + ZB_POINT_S_MIN);
		v->zp.t = (GLint)(v->tex_coord.Y * (ZB_POINT_T_MAX - ZB_POINT_T_MIN) + ZB_POINT_T_MIN);
	}
}

static void gl_add_select1(GLContext* c, GLint z1, GLint z2, GLint z3) {
	GLint min, max;
	min = max = z1;
	if (z2 < min)
		min = z2;
	if (z3 < min)
		min = z3;
	if (z2 > max)
		max = z2;
	if (z3 > max)
		max = z3;

	gl_add_select(c, 0xffffffff - min, 0xffffffff - max);
}

/* point */

void gl_draw_point(GLContext* c, GLVertex* p0) {
	if (p0->clip_code == 0) {
		if (c->render_mode == GL_SELECT) {
			gl_add_select(c, p0->zp.z, p0->zp.z);
		} else {
			ZB_plot(c->zb, &p0->zp);
		}
	}
}

/* line */

static inline void GLinterpolate(GLVertex* q, GLVertex* p0, GLVertex* p1, GLfloat t) {
	q->pc.X = p0->pc.X + (p1->pc.X - p0->pc.X) * t;
	q->pc.Y = p0->pc.Y + (p1->pc.Y - p0->pc.Y) * t;
	q->pc.Z = p0->pc.Z + (p1->pc.Z - p0->pc.Z) * t;
	q->pc.W = p0->pc.W + (p1->pc.W - p0->pc.W) * t;

	q->color.v[0] = p0->color.v[0] + (p1->color.v[0] - p0->color.v[0]) * t;
	q->color.v[1] = p0->color.v[1] + (p1->color.v[1] - p0->color.v[1]) * t;
	q->color.v[2] = p0->color.v[2] + (p1->color.v[2] - p0->color.v[2]) * t;
}

/*
 * Line Clipping
 */

/* Line Clipping algorithm from 'Computer Graphics', Principles and
   Practice */
static inline GLint ClipLine1(GLfloat denom, GLfloat num, GLfloat* tmin, GLfloat* tmax) {
	GLfloat t;

	if (denom > 0) {
		t = num / denom;
		if (t > *tmax)
			return 0;
		if (t > *tmin)
			*tmin = t;
	} else if (denom < 0) {
		t = num / denom;
		if (t < *tmin)
			return 0;
		if (t < *tmax)
			*tmax = t;
	} else if (num > 0)
		return 0;
	return 1;
}

void gl_draw_line(GLContext* c, GLVertex* p1, GLVertex* p2) {
	GLfloat dx, dy, dz, dw, x1, y1, z1, w1;
	GLfloat tmin, tmax;
	GLVertex q1, q2;
	GLint cc1, cc2;

	cc1 = p1->clip_code;
	cc2 = p2->clip_code;

	if ((cc1 | cc2) == 0) {
		if (c->render_mode == GL_SELECT) {
			gl_add_select1(c, p1->zp.z, p2->zp.z, p2->zp.z);
		} else {
			if (c->zb->depth_test)
				ZB_line_z(c->zb, &p1->zp, &p2->zp);
			else
				ZB_line(c->zb, &p1->zp, &p2->zp);
		}
	} else if ((cc1 & cc2) != 0) {
		return;
	} else {
		dx = p2->pc.X - p1->pc.X;
		dy = p2->pc.Y - p1->pc.Y;
		dz = p2->pc.Z - p1->pc.Z;
		dw = p2->pc.W - p1->pc.W;
		x1 = p1->pc.X;
		y1 = p1->pc.Y;
		z1 = p1->pc.Z;
		w1 = p1->pc.W;

		tmin = 0;
		tmax = 1;
		if (ClipLine1(dx + dw, -x1 - w1, &tmin, &tmax) && ClipLine1(-dx + dw, x1 - w1, &tmin, &tmax) && ClipLine1(dy + dw, -y1 - w1, &tmin, &tmax) &&
			ClipLine1(-dy + dw, y1 - w1, &tmin, &tmax) && ClipLine1(dz + dw, -z1 - w1, &tmin, &tmax) && ClipLine1(-dz + dw, z1 - w1, &tmin, &tmax)) {

			GLinterpolate(&q1, p1, p2, tmin);
			GLinterpolate(&q2, p1, p2, tmax);
			gl_transform_to_viewport(c, &q1);
			gl_transform_to_viewport(c, &q2);

			if (c->zb->depth_test)
				ZB_line_z(c->zb, &q1.zp, &q2.zp);
			else
				ZB_line(c->zb, &q1.zp, &q2.zp);
		}
	}
}

/* triangle */

/*
 * Clipping
 */

/* We clip the segment [a,b] against the 6 planes of the normal volume.
 * We compute the point 'c' of GLintersection and the value of the parameter 't'
 * of the GLintersection if x=a+t(b-a).
 */

#define clip_func(name, sign, dir, dir1, dir2)                                                                                                                 \
	static GLfloat name(V4* c, V4* a, V4* b) {                                                                                                                 \
		GLfloat t, dX, dY, dZ, dW, den;                                                                                                                        \
		dX = (b->X - a->X);                                                                                                                                    \
		dY = (b->Y - a->Y);                                                                                                                                    \
		dZ = (b->Z - a->Z);                                                                                                                                    \
		dW = (b->W - a->W);                                                                                                                                    \
		den = -(sign d##dir) + dW;                                                                                                                             \
		if (den == 0)                                                                                                                                          \
			t = 0;                                                                                                                                             \
		else                                                                                                                                                   \
			t = (sign a->dir - a->W) / den;                                                                                                                    \
		c->dir1 = a->dir1 + t * d##dir1;                                                                                                                       \
		c->dir2 = a->dir2 + t * d##dir2;                                                                                                                       \
		c->W = a->W + t * dW;                                                                                                                                  \
		c->dir = sign c->W;                                                                                                                                    \
		return t;                                                                                                                                              \
	}

clip_func(clip_xmin, -, X, Y, Z)

	clip_func(clip_xmax, +, X, Y, Z)

		clip_func(clip_ymin, -, Y, X, Z)

			clip_func(clip_ymax, +, Y, X, Z)

				clip_func(clip_zmin, -, Z, X, Y)

					clip_func(clip_zmax, +, Z, X, Y)

						GLfloat (*clip_proc[6])(V4*, V4*, V4*) = {clip_xmin, clip_xmax, clip_ymin, clip_ymax, clip_zmin, clip_zmax};

static inline void updateTmp(GLContext* c, GLVertex* q, GLVertex* p0, GLVertex* p1, GLfloat t) {
	{
		q->color.v[0] = p0->color.v[0] + (p1->color.v[0] - p0->color.v[0]) * t;
		q->color.v[1] = p0->color.v[1] + (p1->color.v[1] - p0->color.v[1]) * t;
		q->color.v[2] = p0->color.v[2] + (p1->color.v[2] - p0->color.v[2]) * t;
		q->zp.r = p0->zp.r + (p1->zp.r - p0->zp.r) * t;
		q->zp.g = p0->zp.g + (p1->zp.g - p0->zp.g) * t;
		q->zp.b = p0->zp.b + (p1->zp.b - p0->zp.b) * t;
		// q->color.v[3]=p0->color.v[3] + (p1->color.v[3] - p0->color.v[3])*t;
		// tgl_warning("\np0 Components are %f, %f, %f", p0->color.v[0], p0->color.v[1], p0->color.v[2]);
		// tgl_warning("\nZbuffer point r,g,b for p0 are: %d %d %d",p0->zp.r, p0->zp.g,p0->zp.b);
		// tgl_warning("\n~\nNew Components are %f, %f, %f", q->color.v[0], q->color.v[1], q->color.v[2]);
		// tgl_warning("\nZbuffer point r,g,b for new point are: %d %d %d",q->zp.r, q->zp.g,q->zp.b);
		/// *
	}
	//	*/
	if (c->texture_2d_enabled) {
		q->tex_coord.X = p0->tex_coord.X + (p1->tex_coord.X - p0->tex_coord.X) * t;
		q->tex_coord.Y = p0->tex_coord.Y + (p1->tex_coord.Y - p0->tex_coord.Y) * t;
	}

	q->clip_code = gl_clipcode(q->pc.X, q->pc.Y, q->pc.Z, q->pc.W);
	if (q->clip_code == 0)
		gl_transform_to_viewport(c, q);
}

static void gl_draw_triangle_clip(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2, GLint clip_bit);

void gl_draw_triangle(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
	GLint co, c_and, cc[3], front;
	GLfloat norm;

	cc[0] = p0->clip_code;
	cc[1] = p1->clip_code;
	cc[2] = p2->clip_code;

	co = cc[0] | cc[1] | cc[2];

	/* we handle the non clipped case here to go faster */
	if (co == 0) {

		norm = (GLfloat)(p1->zp.x - p0->zp.x) * (GLfloat)(p2->zp.y - p0->zp.y) - (GLfloat)(p2->zp.x - p0->zp.x) * (GLfloat)(p1->zp.y - p0->zp.y);

		if (norm == 0)
			return;

		front = norm < 0.0;
		front = front ^ c->current_front_face;

		/* back face culling */
		if (c->cull_face_enabled) {
			/* most used case first */
			if (c->current_cull_face == GL_BACK) {
				if (front == 0)
					return;
				c->draw_triangle_front(c, p0, p1, p2);
			} else if (c->current_cull_face == GL_FRONT) {
				if (front != 0)
					return;
				c->draw_triangle_back(c, p0, p1, p2);
			} else {
				return;
			}
		} else {
			/* no culling */
			if (front) {
				c->draw_triangle_front(c, p0, p1, p2);
			} else {
				c->draw_triangle_back(c, p0, p1, p2);
			}
		}
	} else {
		c_and = cc[0] & cc[1] & cc[2];
		if (c_and == 0) { // Don't draw a triangle with no points
			gl_draw_triangle_clip(c, p0, p1, p2, 0);
		}
	}
}

static void gl_draw_triangle_clip(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2, GLint clip_bit) {
	GLint co, c_and, co1, cc[3], edge_flag_tmp, clip_mask;
	GLVertex tmp1, tmp2, *q[3];
	GLfloat tt;

	cc[0] = p0->clip_code;
	cc[1] = p1->clip_code;
	cc[2] = p2->clip_code;

	co = cc[0] | cc[1] | cc[2];
	if (co == 0) {
		gl_draw_triangle(c, p0, p1, p2);
	} else {
		c_and = cc[0] & cc[1] & cc[2];
		/* the triangle is completely outside */
		if (c_and != 0)
			return;

		/* find the next direction to clip */
		while (clip_bit < 6 && (co & (1 << clip_bit)) == 0) {
			clip_bit++;
		}

		/* this test can be true only in case of rounding errors */
		if (clip_bit == 6) {
#if 0
      tgl_warning("Error:\n");
      tgl_warning("%f %f %f %f\n",p0->pc.X,p0->pc.Y,p0->pc.Z,p0->pc.W);
      tgl_warning("%f %f %f %f\n",p1->pc.X,p1->pc.Y,p1->pc.Z,p1->pc.W);
      tgl_warning("%f %f %f %f\n",p2->pc.X,p2->pc.Y,p2->pc.Z,p2->pc.W);
#endif
			return;
		}

		clip_mask = 1 << clip_bit;
		co1 = (cc[0] ^ cc[1] ^ cc[2]) & clip_mask;

		if (co1) {
			/* one point outside */

			if (cc[0] & clip_mask) {
				q[0] = p0;
				q[1] = p1;
				q[2] = p2;
			} else if (cc[1] & clip_mask) {
				q[0] = p1;
				q[1] = p2;
				q[2] = p0;
			} else {
				q[0] = p2;
				q[1] = p0;
				q[2] = p1;
			}

			tt = clip_proc[clip_bit](&tmp1.pc, &q[0]->pc, &q[1]->pc);
			updateTmp(c, &tmp1, q[0], q[1], tt);

			tt = clip_proc[clip_bit](&tmp2.pc, &q[0]->pc, &q[2]->pc);
			updateTmp(c, &tmp2, q[0], q[2], tt);

			tmp1.edge_flag = q[0]->edge_flag;
			edge_flag_tmp = q[2]->edge_flag;
			q[2]->edge_flag = 0;
			gl_draw_triangle_clip(c, &tmp1, q[1], q[2], clip_bit + 1);

			tmp2.edge_flag = 1;
			tmp1.edge_flag = 0;
			q[2]->edge_flag = edge_flag_tmp;
			gl_draw_triangle_clip(c, &tmp2, &tmp1, q[2], clip_bit + 1);
		} else {
			/* two points outside */

			if ((cc[0] & clip_mask) == 0) {
				q[0] = p0;
				q[1] = p1;
				q[2] = p2;
			} else if ((cc[1] & clip_mask) == 0) {
				q[0] = p1;
				q[1] = p2;
				q[2] = p0;
			} else {
				q[0] = p2;
				q[1] = p0;
				q[2] = p1;
			}

			tt = clip_proc[clip_bit](&tmp1.pc, &q[0]->pc, &q[1]->pc);
			updateTmp(c, &tmp1, q[0], q[1], tt);

			tt = clip_proc[clip_bit](&tmp2.pc, &q[0]->pc, &q[2]->pc);
			updateTmp(c, &tmp2, q[0], q[2], tt);

			tmp1.edge_flag = 1;
			tmp2.edge_flag = q[2]->edge_flag;
			gl_draw_triangle_clip(c, q[0], &tmp1, &tmp2, clip_bit + 1);
		}
	}
}

void gl_draw_triangle_select(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) { gl_add_select1(c, p0->zp.z, p1->zp.z, p2->zp.z); }

#ifdef PROFILE
int count_triangles, count_triangles_textured, count_pixels;
#endif

void gl_draw_triangle_fill(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
	// puts("\n <yes, it's draw_triangle_fill>");
#ifdef PROFILE
	{
		GLint norm;
		assert(p0->zp.x >= 0 && p0->zp.x < c->zb->xsize);
		assert(p0->zp.y >= 0 && p0->zp.y < c->zb->ysize);
		assert(p1->zp.x >= 0 && p1->zp.x < c->zb->xsize);
		assert(p1->zp.y >= 0 && p1->zp.y < c->zb->ysize);
		assert(p2->zp.x >= 0 && p2->zp.x < c->zb->xsize);
		assert(p2->zp.y >= 0 && p2->zp.y < c->zb->ysize);

		norm = (p1->zp.x - p0->zp.x) * (p2->zp.y - p0->zp.y) - (p2->zp.x - p0->zp.x) * (p1->zp.y - p0->zp.y);
		count_pixels += abs(norm) / 2;
		count_triangles++;
	}
#endif

	if (c->texture_2d_enabled) {
#ifdef PROFILE
		count_triangles_textured++;
#endif
		ZB_setTexture(c->zb, c->current_texture->images[0].pixmap);
#if TGL_FEATURE_BLEND == 1
		if(c->zb->enable_blend) 
			ZB_fillTriangleMappingPerspective(c->zb, &p0->zp, &p1->zp, &p2->zp);
		else 
			ZB_fillTriangleMappingPerspectiveNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
#else
		ZB_fillTriangleMappingPerspectiveNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
#endif
	} else if (c->current_shade_model == GL_SMOOTH) {
		//ZB_fillTriangleSmooth(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#if TGL_FEATURE_BLEND == 1
				if(c->zb->enable_blend) 
					ZB_fillTriangleSmooth(c->zb, &p0->zp, &p1->zp, &p2->zp);
				else 
					ZB_fillTriangleSmoothNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#else
				ZB_fillTriangleSmoothNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#endif
	} else {
		//ZB_fillTriangleFlat(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#if TGL_FEATURE_BLEND == 1
				if(c->zb->enable_blend) 
					ZB_fillTriangleFlat(c->zb, &p0->zp, &p1->zp, &p2->zp);
				else 
					ZB_fillTriangleFlatNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#else
				ZB_fillTriangleFlatNOBLEND(c->zb, &p0->zp, &p1->zp, &p2->zp);
		#endif
	}
}

/* Render a clipped triangle in line mode */

void gl_draw_triangle_line(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
	if (c->zb->depth_test) {
		if (p0->edge_flag)
			ZB_line_z(c->zb, &p0->zp, &p1->zp);
		if (p1->edge_flag)
			ZB_line_z(c->zb, &p1->zp, &p2->zp);
		if (p2->edge_flag)
			ZB_line_z(c->zb, &p2->zp, &p0->zp);
	} else {
		if (p0->edge_flag)
			ZB_line(c->zb, &p0->zp, &p1->zp);
		if (p1->edge_flag)
			ZB_line(c->zb, &p1->zp, &p2->zp);
		if (p2->edge_flag)
			ZB_line(c->zb, &p2->zp, &p0->zp);
	}
}

/* Render a clipped triangle in point mode */
void gl_draw_triangle_point(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
	if (p0->edge_flag)
		ZB_plot(c->zb, &p0->zp);
	if (p1->edge_flag)
		ZB_plot(c->zb, &p1->zp);
	if (p2->edge_flag)
		ZB_plot(c->zb, &p2->zp);
}