ref: 2298e130a5cf4bbf8d828cca6ed3902da8faaa83
dir: /src/clip.c/
#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) {
GLuint 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->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->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) {
if (c->current_shade_model == GL_SMOOTH) {
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;
// printf("\np0 Components are %f, %f, %f", p0->color.v[0], p0->color.v[1], p0->color.v[2]);
// printf("\nZbuffer point r,g,b for p0 are: %d %d %d",p0->zp.r, p0->zp.g,p0->zp.b);
// printf("\n~\nNew Components are %f, %f, %f", q->color.v[0], q->color.v[1], q->color.v[2]);
// printf("\nZbuffer point r,g,b for new point are: %d %d %d",q->zp.r, q->zp.g,q->zp.b);
/// *
} else {
q->color.v[0] = p0->color.v[0];
q->color.v[1] = p0->color.v[1];
q->color.v[2] = p0->color.v[2];
q->zp.r = p0->zp.r;
q->zp.g = p0->zp.g;
q->zp.b = p0->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
printf("Error:\n");
printf("%f %f %f %f\n",p0->pc.X,p0->pc.Y,p0->pc.Z,p0->pc.W);
printf("%f %f %f %f\n",p1->pc.X,p1->pc.Y,p1->pc.Z,p1->pc.W);
printf("%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);
ZB_fillTriangleMappingPerspective(c->zb, &p0->zp, &p1->zp, &p2->zp);
} else if (c->current_shade_model == GL_SMOOTH) {
ZB_fillTriangleSmooth(c->zb, &p0->zp, &p1->zp, &p2->zp);
} else {
ZB_fillTriangleFlat(c->zb, &p0->zp, &p1->zp, &p2->zp);
}
}
/* Render a clipped triangle in line mode */
void gl_draw_triangle_line(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
if (c->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);
}