a

simtools/grid2.cpp

@@ -20,10 +20,13 @@ std::vector<std::vector<Vec3>> gridToPixels(const Sim2& sim, int width, int heig
         int x = static_cast<int>(pos.x);
         int y = static_cast<int>(pos.y);
         
+        // Flip Y coordinate to make (0,0) bottom-left instead of top-left
+        int flippedY = height - 1 - y;
+        
         // Only draw if within bounds
-        if (x >= 0 && x < width && y >= 0 && y < height) {
+        if (x >= 0 && x < width && flippedY >= 0 && flippedY < height) {
             // Convert Vec4 (RGBA) to Vec3 (RGB)
-            pixels[y][x] = Vec3(color.x, color.y, color.z);
+            pixels[flippedY][x] = Vec3(color.x, color.y, color.z);
         }
     }
     
@@ -31,35 +34,44 @@ std::vector<std::vector<Vec3>> gridToPixels(const Sim2& sim, int width, int heig
 }
 
 int main() {
-    const int FRAME_COUNT = 60;
-    const float TOTAL_TIME = 1.0f; // 1 second
+    const int FRAME_COUNT = 120; // Increased frame count for longer animation
+    const float TOTAL_TIME = 4.0f; // Increased to 4 seconds for more movement
     const float TIME_STEP = TOTAL_TIME / FRAME_COUNT;
     
     // Create output directory
     std::filesystem::create_directories("output");
     
-    // Create a simulation with 50x30 grid and gravity
-    Sim2 sim(50, 30, Vec2(0, -9.8f));
+    // Create a simulation with 512x512 grid and SCALED gravity
+    // Scale gravity by ~17x (512/30 ≈ 17) to account for larger grid
+    Sim2 sim(512, 512, Vec2(0, -9.8f * 17.0f));
     
-    // Create some objects
-    auto ball1 = sim.createBall(Vec2(10, 25), 3.0f, Vec4(1.0f, 0.5f, 0.0f, 1.0f), 1.0f); // Orange ball
-    auto ball2 = sim.createBall(Vec2(30, 20), 2.0f, Vec4(0.5f, 0.8f, 1.0f, 1.0f), 0.5f); // Blue ball
+    // Create some objects - adjust positions and sizes for larger grid
+    auto ball1 = sim.createBall(Vec2(100, 400), 40.0f, Vec4(1.0f, 0.5f, 0.0f, 1.0f), 1.0f); // Orange ball
+    auto ball2 = sim.createBall(Vec2(300, 450), 35.0f, Vec4(0.5f, 0.8f, 1.0f, 1.0f), 0.8f); // Blue ball
     
-    // Create ground
-    auto ground = sim.createGround(Vec2(0, 0), 50, Vec4(0.0f, 1.0f, 0.0f, 1.0f)); // Green ground
+    // Give initial velocities to make movement more visible
+    ball1->setVelocity(Vec2(50.0f, 0.0f)); // Rightward velocity
+    ball2->setVelocity(Vec2(-30.0f, 0.0f)); // Leftward velocity
+    
+    // Create ground - higher up so we can see falling
+    auto ground = sim.createGround(Vec2(0, 0), 512, Vec4(0.0f, 1.0f, 0.0f, 1.0f)); // Green ground
+
+    // auto realground = sim.createGround(Vec2(0, 512), 512, Vec4(0.0f, 1.0f, 0.0f, 1.0f)); // Green ground
     
     // Create walls
-    auto leftWall = sim.createWall(Vec2(0, 1), 29, Vec4(0.3f, 0.3f, 0.7f, 1.0f)); // Blue walls
-    auto rightWall = sim.createWall(Vec2(49, 1), 29, Vec4(0.3f, 0.3f, 0.7f, 1.0f));
+    auto leftWall = sim.createWall(Vec2(0, 51), 461, Vec4(0.3f, 0.3f, 0.7f, 1.0f)); // Blue walls (511-50=461)
+    auto rightWall = sim.createWall(Vec2(511, 51), 461, Vec4(0.3f, 0.3f, 0.7f, 1.0f));
+
     
     // Set world bounds
-    sim.setWorldBounds(Vec2(0, 0), Vec2(49, 29));
+    sim.setWorldBounds(Vec2(0, 0), Vec2(511, 511));
     
-    // Simulation parameters
-    sim.setElasticity(0.8f); // Bouncy
-    sim.setFriction(0.05f);  // Low friction
+    // Simulation parameters - adjust for more visible movement
+    sim.setElasticity(0.7f); // Slightly less bouncy
+    sim.setFriction(0.02f);  // Very low friction
     
     std::cout << "Rendering " << FRAME_COUNT << " frames over " << TOTAL_TIME << " seconds..." << std::endl;
+    std::cout << "Gravity: " << sim.getGlobalGravity().y << " px/s²" << std::endl;
     
     // Run simulation and save frames
     for (int frame = 0; frame < FRAME_COUNT; ++frame) {
@@ -67,7 +79,7 @@ int main() {
         sim.update(TIME_STEP);
         
         // Convert simulation state to pixel data
-        auto pixels = gridToPixels(sim, 50, 30);
+        auto pixels = gridToPixels(sim, 512, 512);
         
         // Create filename with zero-padded frame number
         std::ostringstream filename;
@@ -75,7 +87,9 @@ int main() {
         
         // Save as BMP
         if (BMPWriter::saveBMP(filename.str(), pixels)) {
-            std::cout << "Saved frame " << frame << " to " << filename.str() << std::endl;
+            if (frame % 10 == 0) { // Only print every 10 frames to reduce spam
+                std::cout << "Saved frame " << frame << " to " << filename.str() << std::endl;
+            }
         } else {
             std::cerr << "Failed to save frame " << frame << std::endl;
         }

simtools/sim2.hpp

@@ -322,6 +322,9 @@ private:
                 Vec2 worldPos = objPos + positions[i];
                 Vec2 gridPos = worldPos.round();
                 
+                // Flip Y coordinate to make (0,0) bottom-left
+                gridPos.y = height - 1 - gridPos.y;
+                
                 // Only add if within grid bounds
                 if (gridPos.x >= 0 && gridPos.x < width && 
                     gridPos.y >= 0 && gridPos.y < height) {