scene: position sprite tiles from their centre instead of their corner.

src/scene.cpp

@@ -298,10 +298,10 @@ void Scene::RenderTiles() // XXX: rename to Blit()
                 break;
 
         /* Create a vertex array object */
-        VertexBuffer *vb1 = new VertexBuffer(6 * 3 * (n - i) * sizeof(float));
-        float *vertex = (float *)vb1->Lock(0, 0);
-        VertexBuffer *vb2 = new VertexBuffer(6 * 2 * (n - i) * sizeof(float));
-        float *texture = (float *)vb2->Lock(0, 0);
+        VertexBuffer *vb1 = new VertexBuffer(6 * (n - i) * sizeof(vec3));
+        vec3 *vertex = (vec3 *)vb1->Lock(0, 0);
+        VertexBuffer *vb2 = new VertexBuffer(6 * (n - i) * sizeof(vec2));
+        vec2 *texture = (vec2 *)vb2->Lock(0, 0);
 
         data->m_tile_bufs.Push(vb1);
         data->m_tile_bufs.Push(vb2);
@@ -311,7 +311,7 @@ void Scene::RenderTiles() // XXX: rename to Blit()
             data->m_tiles[i].tileset->BlitTile(data->m_tiles[j].id,
                             data->m_tiles[j].pos, data->m_tiles[j].o,
                             data->m_tiles[j].scale,
-                            vertex + 18 * (j - i), texture + 12 * (j - i));
+                            vertex + 6 * (j - i), texture + 6 * (j - i));
         }
 
         vb1->Unlock();

src/tileset.cpp

@@ -197,7 +197,7 @@ void TileSet::Unbind()
 }
 
 void TileSet::BlitTile(uint32_t id, vec3 pos, int o, vec2 scale,
-                       float *vertex, float *texture)
+                       vec3 *vertex, vec2 *texture)
 {
     ibox2 pixels = m_data->m_tiles[id].m1;
     box2 texels = m_data->m_tiles[id].m2;
@@ -228,50 +228,30 @@ void TileSet::BlitTile(uint32_t id, vec3 pos, int o, vec2 scale,
     dty *= 126.f / 128.f;
 #endif
 
+    vec3 extent_x = 0.5f * vec3(dx, 0.f, 0.f);
+    vec3 extent_y = 0.5f * vec3(0.f, dy, dz);
+    vec3 center = pos + extent_x + extent_y;
+
     if (!m_data->m_image && m_data->m_texture)
     {
-        float tmp[10];
-
-        *vertex++ = pos.x + dx;
-        *vertex++ = pos.y + dy;
-        *vertex++ = pos.z + dz;
-        *texture++ = tx + dtx;
-        *texture++ = ty;
-
-        *vertex++ = tmp[0] = pos.x;
-        *vertex++ = tmp[1] = pos.y + dy;
-        *vertex++ = tmp[2] = pos.z + dz;
-        *texture++ = tmp[3] = tx;
-        *texture++ = tmp[4] = ty;
-
-        *vertex++ = tmp[5] = pos.x + dx;
-        *vertex++ = tmp[6] = pos.y;
-        *vertex++ = tmp[7] = pos.z;
-        *texture++ = tmp[8] = tx + dtx;
-        *texture++ = tmp[9] = ty + dty;
-
-        *vertex++ = tmp[5];
-        *vertex++ = tmp[6];
-        *vertex++ = tmp[7];
-        *texture++ = tmp[8];
-        *texture++ = tmp[9];
-
-        *vertex++ = tmp[0];
-        *vertex++ = tmp[1];
-        *vertex++ = tmp[2];
-        *texture++ = tmp[3];
-        *texture++ = tmp[4];
-
-        *vertex++ = pos.x;
-        *vertex++ = pos.y;
-        *vertex++ = pos.z;
-        *texture++ = tx;
-        *texture++ = ty + dty;
+        *vertex++ = center + extent_x + extent_y;
+        *vertex++ = center - extent_x + extent_y;
+        *vertex++ = center + extent_x - extent_y;
+        *vertex++ = center + extent_x - extent_y;
+        *vertex++ = center - extent_x + extent_y;
+        *vertex++ = center - extent_x - extent_y;
+
+        *texture++ = vec2(tx + dtx, ty);
+        *texture++ = vec2(tx,       ty);
+        *texture++ = vec2(tx + dtx, ty + dty);
+        *texture++ = vec2(tx + dtx, ty + dty);
+        *texture++ = vec2(tx,       ty);
+        *texture++ = vec2(tx,       ty + dty);
     }
     else
     {
-        memset(vertex, 0, 3 * sizeof(float));
-        memset(texture, 0, 2 * sizeof(float));
+        memset(vertex, 0, 6 * sizeof(vec3));
+        memset(texture, 0, 6 * sizeof(vec2));
     }
 }
 

src/tileset.h

@@ -53,7 +53,7 @@ public:
     void Bind();
     void Unbind();
     void BlitTile(uint32_t id, vec3 pos, int o, vec2 scale,
-                  float *vertex, float *texture);
+                  vec3 *vertex, vec2 *texture);
 
 private:
     void Init(char const *path);