// r_aclip.c: clip routines for drawing Alias models directly to the screen

#include "quakedef.h"
#include "r_local.h"
#include "d_local.h"

static finalvert_t fv[2][8];
static auxvert_t av[8];

void R_AliasProjectFinalVert(finalvert_t * fv, auxvert_t * av);
void R_Alias_clip_top(finalvert_t * pfv0, finalvert_t * pfv1,
		      finalvert_t * out);
void R_Alias_clip_bottom(finalvert_t * pfv0, finalvert_t * pfv1,
			 finalvert_t * out);
void R_Alias_clip_left(finalvert_t * pfv0, finalvert_t * pfv1,
		       finalvert_t * out);
void R_Alias_clip_right(finalvert_t * pfv0, finalvert_t * pfv1,
			finalvert_t * out);


/*
================
R_Alias_clip_z

pfv0 is the unclipped vertex, pfv1 is the z-clipped vertex
================
*/
void R_Alias_clip_z(finalvert_t * pfv0, finalvert_t * pfv1,
		    finalvert_t * out)
{
    float scale;
    auxvert_t *pav0, *pav1, avout;

    pav0 = &av[pfv0 - &fv[0][0]];
    pav1 = &av[pfv1 - &fv[0][0]];

    if (pfv0->v[1] >= pfv1->v[1]) {
	scale = (ALIAS_Z_CLIP_PLANE - pav0->fv[2]) /
	    (pav1->fv[2] - pav0->fv[2]);

	avout.fv[0] = pav0->fv[0] + (pav1->fv[0] - pav0->fv[0]) * scale;
	avout.fv[1] = pav0->fv[1] + (pav1->fv[1] - pav0->fv[1]) * scale;
	avout.fv[2] = ALIAS_Z_CLIP_PLANE;

	out->v[2] = pfv0->v[2] + (pfv1->v[2] - pfv0->v[2]) * scale;
	out->v[3] = pfv0->v[3] + (pfv1->v[3] - pfv0->v[3]) * scale;
	out->v[4] = pfv0->v[4] + (pfv1->v[4] - pfv0->v[4]) * scale;
    } else {
	scale = (ALIAS_Z_CLIP_PLANE - pav1->fv[2]) /
	    (pav0->fv[2] - pav1->fv[2]);

	avout.fv[0] = pav1->fv[0] + (pav0->fv[0] - pav1->fv[0]) * scale;
	avout.fv[1] = pav1->fv[1] + (pav0->fv[1] - pav1->fv[1]) * scale;
	avout.fv[2] = ALIAS_Z_CLIP_PLANE;

	out->v[2] = pfv1->v[2] + (pfv0->v[2] - pfv1->v[2]) * scale;
	out->v[3] = pfv1->v[3] + (pfv0->v[3] - pfv1->v[3]) * scale;
	out->v[4] = pfv1->v[4] + (pfv0->v[4] - pfv1->v[4]) * scale;
    }

    R_AliasProjectFinalVert(out, &avout);

    if (out->v[0] < r_refdef.aliasvrect.x)
	out->flags |= ALIAS_LEFT_CLIP;
    if (out->v[1] < r_refdef.aliasvrect.y)
	out->flags |= ALIAS_TOP_CLIP;
    if (out->v[0] > r_refdef.aliasvrectright)
	out->flags |= ALIAS_RIGHT_CLIP;
    if (out->v[1] > r_refdef.aliasvrectbottom)
	out->flags |= ALIAS_BOTTOM_CLIP;
}


void R_Alias_clip_left(finalvert_t * pfv0, finalvert_t * pfv1,
		       finalvert_t * out)
{
    float scale;
    int i;

    if (pfv0->v[1] >= pfv1->v[1]) {
	scale = (float) (r_refdef.aliasvrect.x - pfv0->v[0]) /
	    (pfv1->v[0] - pfv0->v[0]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv0->v[i] + (pfv1->v[i] - pfv0->v[i]) * scale + 0.5;
    } else {
	scale = (float) (r_refdef.aliasvrect.x - pfv1->v[0]) /
	    (pfv0->v[0] - pfv1->v[0]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv1->v[i] + (pfv0->v[i] - pfv1->v[i]) * scale + 0.5;
    }
}


void R_Alias_clip_right(finalvert_t * pfv0, finalvert_t * pfv1,
			finalvert_t * out)
{
    float scale;
    int i;

    if (pfv0->v[1] >= pfv1->v[1]) {
	scale = (float) (r_refdef.aliasvrectright - pfv0->v[0]) /
	    (pfv1->v[0] - pfv0->v[0]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv0->v[i] + (pfv1->v[i] - pfv0->v[i]) * scale + 0.5;
    } else {
	scale = (float) (r_refdef.aliasvrectright - pfv1->v[0]) /
	    (pfv0->v[0] - pfv1->v[0]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv1->v[i] + (pfv0->v[i] - pfv1->v[i]) * scale + 0.5;
    }
}


void R_Alias_clip_top(finalvert_t * pfv0, finalvert_t * pfv1,
		      finalvert_t * out)
{
    float scale;
    int i;

    if (pfv0->v[1] >= pfv1->v[1]) {
	scale = (float) (r_refdef.aliasvrect.y - pfv0->v[1]) /
	    (pfv1->v[1] - pfv0->v[1]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv0->v[i] + (pfv1->v[i] - pfv0->v[i]) * scale + 0.5;
    } else {
	scale = (float) (r_refdef.aliasvrect.y - pfv1->v[1]) /
	    (pfv0->v[1] - pfv1->v[1]);
	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv1->v[i] + (pfv0->v[i] - pfv1->v[i]) * scale + 0.5;
    }
}


void R_Alias_clip_bottom(finalvert_t * pfv0, finalvert_t * pfv1,
			 finalvert_t * out)
{
    float scale;
    int i;

    if (pfv0->v[1] >= pfv1->v[1]) {
	scale = (float) (r_refdef.aliasvrectbottom - pfv0->v[1]) /
	    (pfv1->v[1] - pfv0->v[1]);

	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv0->v[i] + (pfv1->v[i] - pfv0->v[i]) * scale + 0.5;
    } else {
	scale = (float) (r_refdef.aliasvrectbottom - pfv1->v[1]) /
	    (pfv0->v[1] - pfv1->v[1]);

	for (i = 0; i < 6; i++)
	    out->v[i] =
		pfv1->v[i] + (pfv0->v[i] - pfv1->v[i]) * scale + 0.5;
    }
}

int R_AliasClip(finalvert_t * in, finalvert_t * out, int flag, int count,
		void (*clip) (finalvert_t * pfv0, finalvert_t * pfv1,
			      finalvert_t * out))
{
    int i, j, k;
    int flags, oldflags;

    j = count - 1;
    k = 0;
    for (i = 0; i < count; j = i, i++) {
	oldflags = in[j].flags & flag;
	flags = in[i].flags & flag;

	if (flags && oldflags)
	    continue;
	if (oldflags ^ flags) {
	    clip(&in[j], &in[i], &out[k]);
	    out[k].flags = 0;
	    if (out[k].v[0] < r_refdef.aliasvrect.x)
		out[k].flags |= ALIAS_LEFT_CLIP;
	    if (out[k].v[1] < r_refdef.aliasvrect.y)
		out[k].flags |= ALIAS_TOP_CLIP;
	    if (out[k].v[0] > r_refdef.aliasvrectright)
		out[k].flags |= ALIAS_RIGHT_CLIP;
	    if (out[k].v[1] > r_refdef.aliasvrectbottom)
		out[k].flags |= ALIAS_BOTTOM_CLIP;
	    k++;
	}
	if (!flags) {
	    out[k] = in[i];
	    k++;
	}
    }

    return k;
}


/*
================
R_AliasClipTriangle
================
*/
void R_AliasClipTriangle(mtriangle_t * ptri)
{
    int i, k, pingpong;
    mtriangle_t mtri;
    unsigned clipflags;

// copy vertexes and fix seam texture coordinates
    if (ptri->facesfront) {
	fv[0][0] = pfinalverts[ptri->vertindex[0]];
	fv[0][1] = pfinalverts[ptri->vertindex[1]];
	fv[0][2] = pfinalverts[ptri->vertindex[2]];
    } else {
	for (i = 0; i < 3; i++) {
	    fv[0][i] = pfinalverts[ptri->vertindex[i]];

	    if (!ptri->facesfront && (fv[0][i].flags & ALIAS_ONSEAM))
		fv[0][i].v[2] += r_affinetridesc.seamfixupX16;
	}
    }

// clip
    clipflags = fv[0][0].flags | fv[0][1].flags | fv[0][2].flags;

    if (clipflags & ALIAS_Z_CLIP) {
	for (i = 0; i < 3; i++)
	    av[i] = pauxverts[ptri->vertindex[i]];

	k = R_AliasClip(fv[0], fv[1], ALIAS_Z_CLIP, 3, R_Alias_clip_z);
	if (k == 0)
	    return;

	pingpong = 1;
	clipflags = fv[1][0].flags | fv[1][1].flags | fv[1][2].flags;
    } else {
	pingpong = 0;
	k = 3;
    }

    if (clipflags & ALIAS_LEFT_CLIP) {
	k = R_AliasClip(fv[pingpong], fv[pingpong ^ 1],
			ALIAS_LEFT_CLIP, k, R_Alias_clip_left);
	if (k == 0)
	    return;

	pingpong ^= 1;
    }

    if (clipflags & ALIAS_RIGHT_CLIP) {
	k = R_AliasClip(fv[pingpong], fv[pingpong ^ 1],
			ALIAS_RIGHT_CLIP, k, R_Alias_clip_right);
	if (k == 0)
	    return;

	pingpong ^= 1;
    }

    if (clipflags & ALIAS_BOTTOM_CLIP) {
	k = R_AliasClip(fv[pingpong], fv[pingpong ^ 1],
			ALIAS_BOTTOM_CLIP, k, R_Alias_clip_bottom);
	if (k == 0)
	    return;

	pingpong ^= 1;
    }

    if (clipflags & ALIAS_TOP_CLIP) {
	k = R_AliasClip(fv[pingpong], fv[pingpong ^ 1],
			ALIAS_TOP_CLIP, k, R_Alias_clip_top);
	if (k == 0)
	    return;

	pingpong ^= 1;
    }

    for (i = 0; i < k; i++) {
	if (fv[pingpong][i].v[0] < r_refdef.aliasvrect.x)
	    fv[pingpong][i].v[0] = r_refdef.aliasvrect.x;
	else if (fv[pingpong][i].v[0] > r_refdef.aliasvrectright)
	    fv[pingpong][i].v[0] = r_refdef.aliasvrectright;

	if (fv[pingpong][i].v[1] < r_refdef.aliasvrect.y)
	    fv[pingpong][i].v[1] = r_refdef.aliasvrect.y;
	else if (fv[pingpong][i].v[1] > r_refdef.aliasvrectbottom)
	    fv[pingpong][i].v[1] = r_refdef.aliasvrectbottom;

	fv[pingpong][i].flags = 0;
    }

// draw triangles
    mtri.facesfront = ptri->facesfront;
    r_affinetridesc.ptriangles = &mtri;
    r_affinetridesc.pfinalverts = fv[pingpong];

// FIXME: do all at once as trifan?
    mtri.vertindex[0] = 0;
    for (i = 1; i < k - 1; i++) {
	mtri.vertindex[1] = i;
	mtri.vertindex[2] = i + 1;
	D_PolysetDraw();
    }
}