mrq/GLdc
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Clip using the w coordinate

Browse Source
This commit is contained in:
Luke Benstead 2018-07-16 08:42:15 +01:00
parent 0d921c3504
commit 60c49f708e
2 changed files with 20 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
GL/clip.c
View File

@ -10,36 +10,15 @@
#include "clip.h"
#include "../containers/aligned_vector.h"
ClipResult clipLineToNearZ(const float* v1, const float* v2, const float dist, float* vout, float* t) {
if(v1[2] < dist && v2[2] < dist) {
// Both behind, no clipping
return CLIP_RESULT_ALL_BEHIND;
}
if(v1[2] > dist && v2[2] > dist) {
return CLIP_RESULT_ALL_IN_FRONT;
}
void clipLineToNearZ(const ClipVertex* v1, const ClipVertex* v2, ClipVertex* vout, float* t) {
*t = (1.0 - v1->w) / (v2->w - v1->w);
float vec [] = {v2[0] - v1[0], v2[1] - v1[1], v2[2] - v1[2]};
float vec [] = {v2->xyz[0] - v1->xyz[0], v2->xyz[1] - v1->xyz[1], v2->xyz[2] - v1->xyz[2]};
/*
* The plane normal will always be pointing down the negative Z so we can simplify the dot products as x and y will always be zero
* the resulting calculation will result in simply -z of the vector
*/
float vecDotP = -vec[2];
/* If the dot product is zero there is no intersection */
if(vecDotP > FLT_MIN || vecDotP < -FLT_MIN) {
*t = (-(dist - v1[2])) / vecDotP;
vout[0] = v1[0] + (vec[0] * (*t));
vout[1] = v1[1] + (vec[1] * (*t));
vout[2] = v1[2] + (vec[2] * (*t));
return (v1[2] >= dist) ? CLIP_RESULT_FRONT_TO_BACK : CLIP_RESULT_BACK_TO_FRONT;
} else {
return CLIP_RESULT_ALL_ON_PLANE;
}
vout->xyz[0] = v1->xyz[0] + (vec[0] * (*t));
vout->xyz[1] = v1->xyz[1] + (vec[1] * (*t));
vout->xyz[2] = v1->xyz[2] + (vec[2] * (*t));
}
static void interpolateFloat(const float v1, const float v2, const float t, float* out) {
@ -112,7 +91,7 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex* v2 = even ? sourceTriangle[1] : sourceTriangle[0];
ClipVertex* v3 = sourceTriangle[2];
uint8_t visible = ((v1->xyz[2] < CLIP_DISTANCE) ? 4 : 0) | ((v2->xyz[2] < CLIP_DISTANCE) ? 2 : 0) | ((v3->xyz[2] < CLIP_DISTANCE) ? 1 : 0);
uint8_t visible = ((v1->w > 0) ? 4 : 0) | ((v2->w > 0) ? 2 : 0) | ((v3->w > 0) ? 1 : 0);
uint8_t startOfStrip = (i == 2) || (outBuffer->size > 2 && ((ClipVertex*) aligned_vector_back(outBuffer))->flags == VERTEX_CMD_EOL);
/* All visible, we're fine! */
@ -132,8 +111,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[3];
clipLineToNearZ(v1->xyz, v2->xyz, CLIP_DISTANCE, output[1].xyz, &t1);
clipLineToNearZ(v1->xyz, v3->xyz, CLIP_DISTANCE, output[2].xyz, &t2);
clipLineToNearZ(v1, v2, &output[1], &t1);
clipLineToNearZ(v1, v3, &output[2], &t2);
interpolateFloat(v1->w, v2->w, t1, &output[1].w);
interpolateFloat(v1->w, v3->w, t2, &output[2].w);
@ -163,8 +142,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[3];
clipLineToNearZ(v2->xyz, v1->xyz, CLIP_DISTANCE, output[0].xyz, &t1);
clipLineToNearZ(v2->xyz, v3->xyz, CLIP_DISTANCE, output[2].xyz, &t2);
clipLineToNearZ(v2, v1, &output[0], &t1);
clipLineToNearZ(v2, v3, &output[2], &t2);
interpolateFloat(v2->w, v1->w, t1, &output[0].w);
interpolateFloat(v2->w, v3->w, t2, &output[2].w);
@ -194,8 +173,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[3];
clipLineToNearZ(v3->xyz, v1->xyz, CLIP_DISTANCE, output[0].xyz, &t1);
clipLineToNearZ(v3->xyz, v2->xyz, CLIP_DISTANCE, output[1].xyz, &t2);
clipLineToNearZ(v3, v1, &output[0], &t1);
clipLineToNearZ(v3, v2, &output[1], &t2);
interpolateFloat(v3->w, v1->w, t1, &output[0].w);
interpolateFloat(v3->w, v2->w, t2, &output[1].w);
@ -225,8 +204,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[4];
clipLineToNearZ(v2->xyz, v3->xyz, CLIP_DISTANCE, output[2].xyz, &t1);
clipLineToNearZ(v1->xyz, v3->xyz, CLIP_DISTANCE, output[3].xyz, &t2);
clipLineToNearZ(v2, v3, &output[2], &t1);
clipLineToNearZ(v1, v3, &output[3], &t2);
interpolateFloat(v2->w, v3->w, t1, &output[2].w);
interpolateFloat(v1->w, v3->w, t2, &output[3].w);
@ -257,8 +236,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[4];
clipLineToNearZ(v1->xyz, v2->xyz, CLIP_DISTANCE, output[0].xyz, &t1);
clipLineToNearZ(v1->xyz, v3->xyz, CLIP_DISTANCE, output[2].xyz, &t2);
clipLineToNearZ(v1, v2, &output[0], &t1);
clipLineToNearZ(v1, v3, &output[2], &t2);
interpolateFloat(v1->w, v2->w, t1, &output[0].w);
interpolateFloat(v1->w, v3->w, t2, &output[2].w);
@ -289,8 +268,8 @@ void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer) {
ClipVertex output[4];
clipLineToNearZ(v1->xyz, v2->xyz, CLIP_DISTANCE, output[1].xyz, &t1);
clipLineToNearZ(v3->xyz, v2->xyz, CLIP_DISTANCE, output[3].xyz, &t2);
clipLineToNearZ(v1, v2, &output[1], &t1);
clipLineToNearZ(v3, v2, &output[3], &t2);
interpolateFloat(v1->w, v2->w, t1, &output[1].w);
interpolateFloat(v3->w, v2->w, t2, &output[3].w);

12
GL/clip.h
View File

@ -39,19 +39,9 @@ typedef struct {
float nES[3]; /* Normal in eye space */
} ClipVertex;
ClipResult clipLineToNearZ(const float* v1, const float* v2, const float dist, float* vout, float* t);
void clipLineToNearZ(const ClipVertex* v1, const ClipVertex* v2, ClipVertex* vout, float* t);
void clipTriangleStrip(AlignedVector* vertices, AlignedVector* outBuffer);
/* FIXME: Why this value? This was copied from libGL because using zero wasn't working right.
*
* I think this is a hack. We should really be clipping against the W coordinate of each vertex... but I'm not sure
* how yet.. this is probably related to the way the z coordinate is mapped to window coordinates or something
*/
#define CLIP_DISTANCE -0.2
#ifdef __cplusplus
}
#endif