From e11e63f273a00b83ebdbdd1d02dad5c645e8203c Mon Sep 17 00:00:00 2001
From: veclavtalica <veclavtalica@tutamail.com>
Date: Sun, 9 Mar 2025 06:24:05 +0300
Subject: [PATCH] /apps/tools/twndel: more plane awareness

---
 apps/tools/twndel/tool.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/apps/tools/twndel/tool.c b/apps/tools/twndel/tool.c
index 1d36ae1..4c46f01 100644
--- a/apps/tools/twndel/tool.c
+++ b/apps/tools/twndel/tool.c
@@ -13,6 +13,9 @@
 /* billboard render to specified angles */
 /* 1 point light primitive lighting */
 
+/* assumptions: */
+/* up is always (0,1,0) */
+
 static State state;
 static bool init;
 
@@ -228,7 +231,7 @@ static bool find_closest_point(uint8_t* object_result, uint16_t *point_result) {
 /* n = normal of a plane */
 static bool vector_plane_intersection(Vec3 o, Vec3 v, Vec3 p, Vec3 n, Vec3 *out) {
     float dot = vec3_dot(n, v);
-    if (dot > FLT_EPSILON) {
+    if (fabsf(dot) > FLT_EPSILON) {
         Vec3 w = vec3_sub(o, p);
         float fac = -vec3_dot(n, w) / dot;
         *out = vec3_add(o, vec3_scale(v, fac));
@@ -263,9 +266,15 @@ static void process_operation_move_point(Operation *op) {
     /* TODO: planes used should depend on looking angle */
     /*       for example, editing from the side makes better use of x/z facing planes */
 
+    /* figure out which planes are angled acutely against the viewing direction */
+    bool y_closer_than_horizon = fabsf(vec3_dot(state.camera_direction, (Vec3){0,1,0})) >= 0.5f;
+
+    Vec3 plane_normal_x = y_closer_than_horizon ? (Vec3){0,1,0} : (Vec3){0,0,1};
+    Vec3 plane_normal_z = y_closer_than_horizon ? (Vec3){0,1,0} : (Vec3){1,0,0};
+
     Vec3 s;
     if (!state.axis_mask[0]) {
-        if (vector_plane_intersection(cam.position, cam.direction, p, (Vec3){0,copysignf(1,cam.direction.y),0}, &s)) {
+        if (vector_plane_intersection(cam.position, cam.direction, p, plane_normal_x, &s)) {
             int16_t xch = (int16_t)(floorf(vec3_dot(vec3_sub(s, p), (Vec3){1,0,0}) * (float)POINTS_PER_METER));
             xch -= xch % state.grid_snap_granularity;
             state.points[op->data.move_point.point].x += xch;
@@ -275,7 +284,7 @@ static void process_operation_move_point(Operation *op) {
     }
 
     if (!state.axis_mask[1]) {
-        if (vector_plane_intersection(cam.position, cam.direction, p, (Vec3){0,0,copysignf(1,cam.direction.z)}, &s)) {
+        if (vector_plane_intersection(cam.position, cam.direction, p, (Vec3){0,0,1}, &s)) {
             int16_t ych = (int16_t)(floorf(vec3_dot(vec3_sub(s, p), (Vec3){0,1,0}) * (float)POINTS_PER_METER));
             ych -= ych % state.grid_snap_granularity;
             state.points[op->data.move_point.point].y += ych;
@@ -285,7 +294,7 @@ static void process_operation_move_point(Operation *op) {
     }
 
     if (!state.axis_mask[2]) {
-        if (vector_plane_intersection(cam.position, cam.direction, p, (Vec3){0,copysignf(1,cam.direction.y),0}, &s)) {
+        if (vector_plane_intersection(cam.position, cam.direction, p, plane_normal_z, &s)) {
             int16_t zch = (int16_t)(floorf(vec3_dot(vec3_sub(s, p), (Vec3){0,0,1}) * (float)POINTS_PER_METER));
             zch -= zch % state.grid_snap_granularity;
             state.points[op->data.move_point.point].z += zch;