/apps/demos/scenery: lock movement direction to a plane

apps/demos/scenery/scenes/ingame.c

@@ -48,12 +48,44 @@ static void process_fly_mode(State *state) {
 }
 
 
+static float height_at(SceneIngame *scn, Vec2 position) {
+    float height0, height1, height2, weight0, weight1, weight2;
+
+    int const x = (int)(HALF_TERRAIN_DISTANCE + (position.x - scn->pos.x));
+    int const y = (int)(HALF_TERRAIN_DISTANCE + (position.y - scn->pos.z));
+
+    height0 = heightmap[x][y];
+    height1 = heightmap[x + 1][y + 1];
+
+    Vec2 incell = { position.x - floorf(position.x), position.y - floorf(position.y) };
+
+    /* who needs barycentric coordinates, am i right? */
+    weight0 = 1 / sqrtf(powf(incell.x, 2) + powf(incell.y, 2));
+    weight1 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(1 - incell.y, 2));
+
+    /* find which triangle we're directly under */
+    /* for this manhattan distance is sufficient */
+    if (incell.x + (1 - incell.y) < (1 - incell.x) + incell.y) {
+        height2 = heightmap[x][y + 1];
+        weight2 = 1 / sqrtf(powf(incell.x, 2) + powf(1 - incell.y, 2));
+    } else {
+        height2 = heightmap[x + 1][y];
+        weight2 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(incell.y, 2));
+    }
+
+    return (height0 * weight0 + height1 * weight1 + height2 * weight2) / (weight0 + weight1 + weight2);
+}
+
+
 static void process_ground_mode(State *state) {
     SceneIngame *scn = (SceneIngame *)state->scene;
 
     DrawCameraFromPrincipalAxesResult dir_and_up =
         draw_camera_from_principal_axes(scn->pos, (float)M_PI_2 * 0.8f, scn->roll, scn->pitch, scn->yaw);
 
+    dir_and_up.direction.y = 0;
+    dir_and_up.direction = vec3_norm(dir_and_up.direction);
+
     const Vec3 right = m_vec_norm(m_vec_cross(dir_and_up.direction, dir_and_up.up));
     const float speed = 0.18f; /* TODO: put this in a better place */
 
@@ -61,35 +93,13 @@ static void process_ground_mode(State *state) {
 
     /* gravity */
     {
-        float height0, height1, height2, weight0, weight1, weight2;
+        float const height = height_at(scn, (Vec2){scn->pos.x, scn->pos.z});
-
-        height0 = heightmap[(int)HALF_TERRAIN_DISTANCE][(int)HALF_TERRAIN_DISTANCE];
-        height1 = heightmap[(int)HALF_TERRAIN_DISTANCE + 1][(int)HALF_TERRAIN_DISTANCE + 1];
-
-        Vec2 incell = { scn->pos.x - floorf(scn->pos.x), scn->pos.z - floorf(scn->pos.z) };
-
-        /* who needs barycentric coordinates, am i right? */
-        weight0 = 1 / sqrtf(powf(incell.x, 2) + powf(incell.y, 2));
-        weight1 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(1 - incell.y, 2));
-
-        /* find which triangle we're directly under */
-        /* for this manhattan distance is sufficient */
-        if (incell.x + (1 - incell.y) < (1 - incell.x) + incell.y) {
-            height2 = heightmap[(int)HALF_TERRAIN_DISTANCE][(int)HALF_TERRAIN_DISTANCE + 1];
-            weight2 = 1 / sqrtf(powf(incell.x, 2) + powf(1 - incell.y, 2));
-        } else {
-            height2 = heightmap[(int)HALF_TERRAIN_DISTANCE + 1][(int)HALF_TERRAIN_DISTANCE];
-            weight2 = 1 / sqrtf(powf(1 - incell.x, 2) + powf(incell.y, 2));
-        }
-
-        float height = (height0 * weight0 + height1 * weight1 + height2 * weight2) / (weight0 + weight1 + weight2);
 
         if (target.y > height + PLAYER_HEIGHT)
             target.y = target.y - 0.4f;
 
         if (target.y < height + PLAYER_HEIGHT)
             target.y = height + PLAYER_HEIGHT;
-
     }
 
     /* movement */
@@ -159,7 +169,10 @@ static void draw_terrain(SceneIngame *scn) {
                             (Vec2){ 0, 0 },
                             (Vec2){ 0, 128 });
 
-            draw_billboard("/assets/grasses/10.png", (Vec3){ (float)x, d1 + 0.1f, (float)y }, (Vec2){0.3f, 0.3f}, (Color){255, 255, 255, 255}, true);
+            draw_billboard("/assets/grasses/10.png",
+                          (Vec3){ (float)x, d0 + 0.15f, (float)y },
+                          (Vec2){0.3f, 0.3f},
+                          (Color){255, 255, 255, 255}, true);
         }
     }
 }