Add screen->world and world->screen functions for 2D; add extended camera2D example (#947)

1 files changed, 37 insertions, 22 deletions

diff --git a/src/core.c b/src/core.c
index c025b2de..987f6e67 100644
--- a/src/core.c
+++ b/src/core.c
@@ -1250,28 +1250,7 @@ void BeginMode2D(Camera2D camera)
     rlLoadIdentity();                   // Reset current matrix (MODELVIEW)
     rlMultMatrixf(MatrixToFloat(screenScaling)); // Apply screen scaling if required
 
-    // The camera in world-space is set by
-    //   1. Move it to target
-    //   2. Rotate by -rotation and scale by (1/zoom)
-    //      When setting higher scale, it's more intuitive for the world to become bigger (= camera become smaller),
-    //      not for the camera getting bigger, hence the invert. Same deal with rotation.
-    //   3. Move it by (-offset);
-    //      Offset defines target transform relative to screen, but since we're effectively "moving" screen (camera)
-    //      we need to do it into opposite direction (inverse transform)
-
-    // Having camera transform in world-space, inverse of it gives the modelview transform.
-    // Since (A*B*C)' = C'*B'*A', the modelview is
-    //   1. Move to offset
-    //   2. Rotate and Scale
-    //   3. Move by -target
-    Matrix matOrigin = MatrixTranslate(-camera.target.x, -camera.target.y, 0.0f);
-    Matrix matRotation = MatrixRotate((Vector3){ 0.0f, 0.0f, 1.0f }, camera.rotation*DEG2RAD);
-    Matrix matScale = MatrixScale(camera.zoom, camera.zoom, 1.0f);
-    Matrix matTranslation = MatrixTranslate(camera.offset.x, camera.offset.y, 0.0f);
-
-    Matrix matTransform = MatrixMultiply(MatrixMultiply(matOrigin, MatrixMultiply(matScale, matRotation)), matTranslation);
-
-    rlMultMatrixf(MatrixToFloat(matTransform));  // Apply transformation to modelview
+    rlMultMatrixf(MatrixToFloat(GetCamera2DMatrix(camera)));  // Apply transformation to modelview
 }
 
 // Ends 2D mode with custom camera
@@ -1502,6 +1481,42 @@ Matrix GetCameraMatrix(Camera camera)
     return MatrixLookAt(camera.position, camera.target, camera.up);
 }
 
+
+Vector2 GetScreenToWorld2D(Vector2 position, Camera2D camera) {
+    Matrix m = MatrixInvert(GetCamera2DMatrix(camera));
+    Vector3 transform = Vector3Transform((Vector3){position.x, position.y, 0}, m);
+    return (Vector2){transform.x, transform.y};
+}
+
+Vector2 GetWorldToScreen2D(Vector2 position, Camera2D camera) {
+    Matrix m = GetCamera2DMatrix(camera);
+    Vector3 transform = Vector3Transform((Vector3){position.x, position.y, 0}, m);
+    return (Vector2){transform.x, transform.y};
+}
+
+Matrix GetCamera2DMatrix(Camera2D camera) {
+    // The camera in world-space is set by
+    //   1. Move it to target
+    //   2. Rotate by -rotation and scale by (1/zoom)
+    //      When setting higher scale, it's more intuitive for the world to become bigger (= camera become smaller),
+    //      not for the camera getting bigger, hence the invert. Same deal with rotation.
+    //   3. Move it by (-offset);
+    //      Offset defines target transform relative to screen, but since we're effectively "moving" screen (camera)
+    //      we need to do it into opposite direction (inverse transform)
+
+    // Having camera transform in world-space, inverse of it gives the modelview transform.
+    // Since (A*B*C)' = C'*B'*A', the modelview is
+    //   1. Move to offset
+    //   2. Rotate and Scale
+    //   3. Move by -target
+    Matrix matOrigin = MatrixTranslate(-camera.target.x, -camera.target.y, 0.0f);
+    Matrix matRotation = MatrixRotate((Vector3){ 0.0f, 0.0f, 1.0f }, camera.rotation*DEG2RAD);
+    Matrix matScale = MatrixScale(camera.zoom, camera.zoom, 1.0f);
+    Matrix matTranslation = MatrixTranslate(camera.offset.x, camera.offset.y, 0.0f);
+    Matrix matTransform = MatrixMultiply(MatrixMultiply(matOrigin, MatrixMultiply(matScale, matRotation)), matTranslation);
+    return matTransform;
+}
+
 // Set target FPS (maximum)
 void SetTargetFPS(int fps)
 {