Imperfections when Bake displacement map to plane if camera is not in front #48550

New Issue

YAFU · 2016-05-30T20:48:45+02:00

YAFU commented

2016-05-30 20:48:45 +02:00

System Information
Kubuntu Linux 64bits, GTX 960

Blender Version
Broken: Perhaps all, I've tried from blender 2.73a until buildbot.

Short description of error
Hi. Sorry if this is not a bug, but I prefer to report just in case. I asked in forum and IRC, but still I could not clear the doubt.
I've been looking for documentation about whether or not it is needed some Camera configuration in Blender internal to bake the displacement map form objets to a plane. Like this answer from Greg Zaal, he does not mention any special camera settings:
https://blender.stackexchange.com/questions/1161/how-to-make-a-displacement-map-from-existing-3d-geometry

I have this concern because with this .blend file:
Displacement map_bi.blend

if I do not set the camera in front and top of the plane, then I get small square/pixels missing in the bake image, like these that another user mentions some years ago:
https://blender.stackexchange.com/questions/18639/small-errors-when-baking-displacement-maps

Exact steps for others to reproduce the error
Open the .blend I shared and bake. Then zoom in the bake image much and you see carefully looking for those little squares.

If you places the camera above (in top view just Ctrl+Alt+NP 0, and no matter if the camera is centered) and bake again, then the imperfections do not appear.

**System Information** Kubuntu Linux 64bits, GTX 960 **Blender Version** Broken: Perhaps all, I've tried from blender 2.73a until buildbot. **Short description of error** Hi. Sorry if this is not a bug, but I prefer to report just in case. I asked in forum and IRC, but still I could not clear the doubt. I've been looking for documentation about whether or not it is needed some Camera configuration in Blender internal to bake the displacement map form objets to a plane. Like this answer from Greg Zaal, he does not mention any special camera settings: https://blender.stackexchange.com/questions/1161/how-to-make-a-displacement-map-from-existing-3d-geometry I have this concern because with this .blend file: [Displacement map_bi.blend](https://archive.blender.org/developer/F315351/Displacement_map_bi.blend) if I do not set the camera in front and top of the plane, then I get small square/pixels missing in the bake image, like these that another user mentions some years ago: https://blender.stackexchange.com/questions/18639/small-errors-when-baking-displacement-maps **Exact steps for others to reproduce the error** Open the .blend I shared and bake. Then zoom in the bake image much and you see carefully looking for those little squares. If you places the camera above (in top view just Ctrl+Alt+NP 0, and no matter if the camera is centered) and bake again, then the imperfections do not appear.

YAFU commented

2016-05-30 20:48:45 +02:00

Changed status to: 'Open'

YAFU commented

2016-05-30 20:48:45 +02:00

Added subscriber: @YAFU

Sergey Sharybin commented

2016-05-31 11:27:17 +02:00

Added subscribers: @brecht, @Sergey

Sergey Sharybin commented

2016-05-31 11:27:17 +02:00

Root of the issue here is non-watertight nature of ray-tri intersection in BI, which is very much similar to what we had in Cycles. The reason why artifacts depends on camera angle is because BI considers all objects to be in camera space when rendering or baking.

Have a quick patch to make intersections watertight:

P359: Snippet for #48550

diff --git a/source/blender/render/intern/include/rayintersection.h b/source/blender/render/intern/include/rayintersection.h
index 3607e66..1935e4e 100644
--- a/source/blender/render/intern/include/rayintersection.h
+++ b/source/blender/render/intern/include/rayintersection.h
@@ -38,6 +38,8 @@
 extern "C" {
 #endif
 
+#include "BLI_math_geom.h"
+
 struct RayObject;
 
 /* Ray Hints */
@@ -101,6 +103,9 @@ typedef struct Isect {
 #ifdef RE_RAYCOUNTER
 	RayCounter *raycounter;
 #endif
+
+	/* Precalculated coefficients for watertight intersection check. */
+	struct IsectRayPrecalc isect_precalc;
 } Isect;
 
 /* ray types */
diff --git a/source/blender/render/intern/raytrace/rayobject.cpp b/source/blender/render/intern/raytrace/rayobject.cpp
index de6b913..66653fd 100644
--- a/source/blender/render/intern/raytrace/rayobject.cpp
+++ b/source/blender/render/intern/raytrace/rayobject.cpp
@@ -138,80 +138,29 @@ MALWAYS_INLINE int vlr_check_bake(Isect *is, ObjectInstanceRen *obi, VlakRen *UN
 
 /* Ray Triangle/Quad Intersection */
 
-MALWAYS_INLINE int isec_tri_quad(float start- [x], float dir- [x], RayFace *face, float uv- [x], float *lambda)
+MALWAYS_INLINE int isec_tri_quad(float start- [x], const struct IsectRayPrecalc *isect_precalc, RayFace *face, float r_uv- [x], float *lambda)
 {
-	float co1- [x], co2- [x], co3- [x], co4[3];
-	float t0- [x], t1- [x], x- [x], r- [x], m- [x], u, v, divdet, det1, l;
-	int quad;
-
-	quad = RE_rayface_isQuad(face);
-
-	copy_v3_v3(co1, face->v1);
-	copy_v3_v3(co2, face->v2);
-	copy_v3_v3(co3, face->v3);
-
-	copy_v3_v3(r, dir);
-
-	/* intersect triangle */
-	sub_v3_v3v3(t0, co3, co2);
-	sub_v3_v3v3(t1, co3, co1);
-
-	cross_v3_v3v3(x, r, t1);
-	divdet = dot_v3v3(t0, x);
-
-	sub_v3_v3v3(m, start, co3);
-	det1 = dot_v3v3(m, x);
-	
-	if (divdet != 0.0f) {
-		divdet = 1.0f / divdet;
-		v = det1 * divdet;
-
-		if (v < RE_RAYTRACE_EPSILON && v > -(1.0f + RE_RAYTRACE_EPSILON)) {
-			float cros[3];
-
-			cross_v3_v3v3(cros, m, t0);
-			u = divdet * dot_v3v3(cros, r);
-
-			if (u < RE_RAYTRACE_EPSILON && (v + u) > -(1.0f + RE_RAYTRACE_EPSILON)) {
-				l = divdet * dot_v3v3(cros, t1);
-
-				/* check if intersection is within ray length */
-				if (l > -RE_RAYTRACE_EPSILON && l < *lambda) {
-					uv- [x] = u;
-					uv- [x] = v;
-					*lambda = l;
-					return 1;
-				}
-			}
+	float uv- [x], l;
+
+	if (isect_ray_tri_watertight_v3(start, isect_precalc, face->v1, face->v2, face->v3, &l, uv)) {
+		/* check if intersection is within ray length */
+		if (l > -RE_RAYTRACE_EPSILON && l < *lambda) {
+			r_uv- [x] = uv[0];
+			r_uv- [x] = uv[1];
+			*lambda = l;
+			return 1;
 		}
 	}
 
 	/* intersect second triangle in quad */
-	if (quad) {
-		copy_v3_v3(co4, face->v4);
-		sub_v3_v3v3(t0, co3, co4);
-		divdet = dot_v3v3(t0, x);
-
-		if (divdet != 0.0f) {
-			divdet = 1.0f / divdet;
-			v = det1 * divdet;
-			
-			if (v < RE_RAYTRACE_EPSILON && v > -(1.0f + RE_RAYTRACE_EPSILON)) {
-				float cros[3];
-
-				cross_v3_v3v3(cros, m, t0);
-				u = divdet * dot_v3v3(cros, r);
-	
-				if (u < RE_RAYTRACE_EPSILON && (v + u) > -(1.0f + RE_RAYTRACE_EPSILON)) {
-					l = divdet * dot_v3v3(cros, t1);
-					
-					if (l > -RE_RAYTRACE_EPSILON && l < *lambda) {
-						uv- [x] = u;
-						uv- [x] = -(1.0f + v + u);
-						*lambda = l;
-						return 2;
-					}
-				}
+	if (RE_rayface_isQuad(face)) {
+		if (isect_ray_tri_watertight_v3(start, isect_precalc, face->v1, face->v3, face->v4, &l, uv)) {
+			/* check if intersection is within ray length */
+			if (l > -RE_RAYTRACE_EPSILON && l < *lambda) {
+				r_uv- [x] = uv[0];
+				r_uv- [x] = uv[1];
+				*lambda = l;
+				return 1;
 			}
 		}
 	}
@@ -221,6 +170,7 @@ MALWAYS_INLINE int isec_tri_quad(float start- [x], float dir- [x], RayFace *face, fl
 
 /* Simpler yes/no Ray Triangle/Quad Intersection */
 
+/* TODO(sergey): Can become watertight. */
 MALWAYS_INLINE int isec_tri_quad_neighbour(float start- [x], float dir- [x], RayFace *face)
 {
 	float co1- [x], co2- [x], co3- [x], co4[3];
@@ -317,7 +267,7 @@ MALWAYS_INLINE int intersect_rayface(RayObject *hit_obj, RayFace *face, Isect *i
 	RE_RC_COUNT(is->raycounter->faces.test);
 
 	dist = is->dist;
-	ok = isec_tri_quad(is->start, is->dir, face, uv, &dist);
+	ok = isec_tri_quad(is->start, &is->isect_precalc, face, uv, &dist);
 
 	if (ok) {
 	
@@ -433,6 +383,9 @@ int RE_rayobject_raycast(RayObject *r, Isect *isec)
 
 int RE_rayobject_intersect(RayObject *r, Isect *i)
 {
+	/* Pre-calculate orientation for watertight intersection checks. */
+	isect_ray_tri_watertight_v3_precalc(&i->isect_precalc, i->dir);
+
 	if (RE_rayobject_isRayFace(r)) {
 		return intersect_rayface(r, (RayFace *) RE_rayobject_align(r), i);
 	}

But there are couple of things:

Since the triangle intersection is now happening in bf_blenlib it's no longer using same SIMD optimization level as the raycatsobject. Perhaps it's not so bad, because SSE2 is now enabled globally for whole Blender and i'm not sure if higher SSE will actually be applyable to triangle intersection.
While it seems to work with this particular file, i'm not sure how to verify it on all other files
Neighbor intersection is not watertight yet. It also seems it can't re-use same pre-calculation because direction is inverted, so it'll be somewhat slower.

@brecht, do you have some strong opinion here?

Root of the issue here is non-watertight nature of ray-tri intersection in BI, which is very much similar to what we had in Cycles. The reason why artifacts depends on camera angle is because BI considers all objects to be in camera space when rendering or baking. Have a quick patch to make intersections watertight: [P359: Snippet for #48550](https://archive.blender.org/developer/P359.txt) ``` diff --git a/source/blender/render/intern/include/rayintersection.h b/source/blender/render/intern/include/rayintersection.h index 3607e66..1935e4e 100644 --- a/source/blender/render/intern/include/rayintersection.h +++ b/source/blender/render/intern/include/rayintersection.h @@ -38,6 +38,8 @@ extern "C" { #endif +#include "BLI_math_geom.h" + struct RayObject; /* Ray Hints */ @@ -101,6 +103,9 @@ typedef struct Isect { #ifdef RE_RAYCOUNTER RayCounter *raycounter; #endif + + /* Precalculated coefficients for watertight intersection check. */ + struct IsectRayPrecalc isect_precalc; } Isect; /* ray types */ diff --git a/source/blender/render/intern/raytrace/rayobject.cpp b/source/blender/render/intern/raytrace/rayobject.cpp index de6b913..66653fd 100644 --- a/source/blender/render/intern/raytrace/rayobject.cpp +++ b/source/blender/render/intern/raytrace/rayobject.cpp @@ -138,80 +138,29 @@ MALWAYS_INLINE int vlr_check_bake(Isect *is, ObjectInstanceRen *obi, VlakRen *UN /* Ray Triangle/Quad Intersection */ -MALWAYS_INLINE int isec_tri_quad(float start- [x], float dir- [x], RayFace *face, float uv- [x], float *lambda) +MALWAYS_INLINE int isec_tri_quad(float start- [x], const struct IsectRayPrecalc *isect_precalc, RayFace *face, float r_uv- [x], float *lambda) { - float co1- [x], co2- [x], co3- [x], co4[3]; - float t0- [x], t1- [x], x- [x], r- [x], m- [x], u, v, divdet, det1, l; - int quad; - - quad = RE_rayface_isQuad(face); - - copy_v3_v3(co1, face->v1); - copy_v3_v3(co2, face->v2); - copy_v3_v3(co3, face->v3); - - copy_v3_v3(r, dir); - - /* intersect triangle */ - sub_v3_v3v3(t0, co3, co2); - sub_v3_v3v3(t1, co3, co1); - - cross_v3_v3v3(x, r, t1); - divdet = dot_v3v3(t0, x); - - sub_v3_v3v3(m, start, co3); - det1 = dot_v3v3(m, x); - - if (divdet != 0.0f) { - divdet = 1.0f / divdet; - v = det1 * divdet; - - if (v < RE_RAYTRACE_EPSILON && v > -(1.0f + RE_RAYTRACE_EPSILON)) { - float cros[3]; - - cross_v3_v3v3(cros, m, t0); - u = divdet * dot_v3v3(cros, r); - - if (u < RE_RAYTRACE_EPSILON && (v + u) > -(1.0f + RE_RAYTRACE_EPSILON)) { - l = divdet * dot_v3v3(cros, t1); - - /* check if intersection is within ray length */ - if (l > -RE_RAYTRACE_EPSILON && l < *lambda) { - uv- [x] = u; - uv- [x] = v; - *lambda = l; - return 1; - } - } + float uv- [x], l; + + if (isect_ray_tri_watertight_v3(start, isect_precalc, face->v1, face->v2, face->v3, &l, uv)) { + /* check if intersection is within ray length */ + if (l > -RE_RAYTRACE_EPSILON && l < *lambda) { + r_uv- [x] = uv[0]; + r_uv- [x] = uv[1]; + *lambda = l; + return 1; } } /* intersect second triangle in quad */ - if (quad) { - copy_v3_v3(co4, face->v4); - sub_v3_v3v3(t0, co3, co4); - divdet = dot_v3v3(t0, x); - - if (divdet != 0.0f) { - divdet = 1.0f / divdet; - v = det1 * divdet; - - if (v < RE_RAYTRACE_EPSILON && v > -(1.0f + RE_RAYTRACE_EPSILON)) { - float cros[3]; - - cross_v3_v3v3(cros, m, t0); - u = divdet * dot_v3v3(cros, r); - - if (u < RE_RAYTRACE_EPSILON && (v + u) > -(1.0f + RE_RAYTRACE_EPSILON)) { - l = divdet * dot_v3v3(cros, t1); - - if (l > -RE_RAYTRACE_EPSILON && l < *lambda) { - uv- [x] = u; - uv- [x] = -(1.0f + v + u); - *lambda = l; - return 2; - } - } + if (RE_rayface_isQuad(face)) { + if (isect_ray_tri_watertight_v3(start, isect_precalc, face->v1, face->v3, face->v4, &l, uv)) { + /* check if intersection is within ray length */ + if (l > -RE_RAYTRACE_EPSILON && l < *lambda) { + r_uv- [x] = uv[0]; + r_uv- [x] = uv[1]; + *lambda = l; + return 1; } } } @@ -221,6 +170,7 @@ MALWAYS_INLINE int isec_tri_quad(float start- [x], float dir- [x], RayFace *face, fl /* Simpler yes/no Ray Triangle/Quad Intersection */ +/* TODO(sergey): Can become watertight. */ MALWAYS_INLINE int isec_tri_quad_neighbour(float start- [x], float dir- [x], RayFace *face) { float co1- [x], co2- [x], co3- [x], co4[3]; @@ -317,7 +267,7 @@ MALWAYS_INLINE int intersect_rayface(RayObject *hit_obj, RayFace *face, Isect *i RE_RC_COUNT(is->raycounter->faces.test); dist = is->dist; - ok = isec_tri_quad(is->start, is->dir, face, uv, &dist); + ok = isec_tri_quad(is->start, &is->isect_precalc, face, uv, &dist); if (ok) { @@ -433,6 +383,9 @@ int RE_rayobject_raycast(RayObject *r, Isect *isec) int RE_rayobject_intersect(RayObject *r, Isect *i) { + /* Pre-calculate orientation for watertight intersection checks. */ + isect_ray_tri_watertight_v3_precalc(&i->isect_precalc, i->dir); + if (RE_rayobject_isRayFace(r)) { return intersect_rayface(r, (RayFace *) RE_rayobject_align(r), i); } ``` But there are couple of things: - Since the triangle intersection is now happening in `bf_blenlib` it's no longer using same SIMD optimization level as the `raycatsobject`. Perhaps it's not so bad, because SSE2 is now enabled globally for whole Blender and i'm not sure if higher SSE will actually be applyable to triangle intersection. - While it seems to work with this particular file, i'm not sure how to verify it on all other files - Neighbor intersection is not watertight yet. It also seems it can't re-use same pre-calculation because direction is inverted, so it'll be somewhat slower. @brecht, do you have some strong opinion here?

Sergey Sharybin self-assigned this 2016-05-31 11:27:30 +02:00

Brecht Van Lommel commented

2016-06-04 00:50:08 +02:00

No strong opinion here, watertight intersection is worth a small slowdown in my opinion.

Sergey Sharybin commented

2016-06-06 13:55:04 +02:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2016-06-06 13:55:04 +02:00

blender-admin commented

2016-06-06 13:55:04 +02:00

This issue was referenced by fd7068ee28

This issue was referenced by fd7068ee2879c949b5b6e9356702e00201988481

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Imperfections when Bake displacement map to plane if camera is not in front #48550