Improve physics and add examples

examples/physics/physac/friction/main.go

@@ -0,0 +1,114 @@
+package main
+
+import (
+	"github.com/gen2brain/raylib-go/physics"
+	"github.com/gen2brain/raylib-go/raylib"
+)
+
+func main() {
+	screenWidth := int32(800)
+	screenHeight := int32(450)
+
+	raylib.SetDebug(true)
+	raylib.SetConfigFlags(raylib.FlagMsaa4xHint)
+	raylib.InitWindow(screenWidth, screenHeight, "Physac [raylib] - physics friction")
+
+	// Physac logo drawing position
+	logoX := screenWidth - raylib.MeasureText("Physac", 30) - 10
+	logoY := int32(15)
+
+	// Initialize physics and default physics bodies
+	physics.Init()
+
+	// Create floor rectangle physics body
+	floor := physics.NewBodyRectangle(raylib.NewVector2(float32(screenWidth)/2, float32(screenHeight)), float32(screenHeight), 100, 10)
+	floor.Enabled = false // Disable body state to convert it to static (no dynamics, but collisions)
+	wall := physics.NewBodyRectangle(raylib.NewVector2(float32(screenWidth)/2, float32(screenHeight)*0.8), 10, 80, 10)
+	wall.Enabled = false // Disable body state to convert it to static (no dynamics, but collisions)
+
+	// Create left ramp physics body
+	rectLeft := physics.NewBodyRectangle(raylib.NewVector2(25, float32(screenHeight)-5), 250, 250, 10)
+	rectLeft.Enabled = false // Disable body state to convert it to static (no dynamics, but collisions)
+	rectLeft.SetRotation(30 * raylib.Deg2rad)
+
+	// Create right ramp  physics body
+	rectRight := physics.NewBodyRectangle(raylib.NewVector2(float32(screenWidth)-25, float32(screenHeight)-5), 250, 250, 10)
+	rectRight.Enabled = false // Disable body state to convert it to static (no dynamics, but collisions)
+	rectRight.SetRotation(330 * raylib.Deg2rad)
+
+	// Create dynamic physics bodies
+	bodyA := physics.NewBodyRectangle(raylib.NewVector2(35, float32(screenHeight)*0.6), 40, 40, 10)
+	bodyA.StaticFriction = 0.1
+	bodyA.DynamicFriction = 0.1
+	bodyA.SetRotation(30 * raylib.Deg2rad)
+
+	bodyB := physics.NewBodyRectangle(raylib.NewVector2(float32(screenWidth)-35, float32(screenHeight)*0.6), 40, 40, 10)
+	bodyB.StaticFriction = 1
+	bodyB.DynamicFriction = 1
+	bodyB.SetRotation(330 * raylib.Deg2rad)
+
+	raylib.SetTargetFPS(60)
+
+	for !raylib.WindowShouldClose() {
+		// Physics steps calculations
+		physics.Update()
+
+		if raylib.IsKeyPressed(raylib.KeyR) { // Reset physics input
+			// Reset dynamic physics bodies position, velocity and rotation
+			bodyA.Position = raylib.NewVector2(35, float32(screenHeight)*0.6)
+			bodyA.Velocity = raylib.NewVector2(0, 0)
+			bodyA.AngularVelocity = 0
+			bodyA.SetRotation(30 * raylib.Deg2rad)
+
+			bodyB.Position = raylib.NewVector2(float32(screenWidth)-35, float32(screenHeight)*0.6)
+			bodyB.Velocity = raylib.NewVector2(0, 0)
+			bodyB.AngularVelocity = 0
+			bodyB.SetRotation(330 * raylib.Deg2rad)
+		}
+
+		raylib.BeginDrawing()
+
+		raylib.ClearBackground(raylib.Black)
+
+		raylib.DrawFPS(screenWidth-90, screenHeight-30)
+
+		// Draw created physics bodies
+		bodiesCount := physics.GetBodiesCount()
+		for i := 0; i < bodiesCount; i++ {
+			body := physics.GetBody(i)
+
+			vertexCount := physics.GetShapeVerticesCount(i)
+			for j := 0; j < vertexCount; j++ {
+				// Get physics bodies shape vertices to draw lines
+				// NOTE: GetShapeVertex() already calculates rotation transformations
+				vertexA := body.GetShapeVertex(j)
+
+				jj := 0
+				if j+1 < vertexCount { // Get next vertex or first to close the shape
+					jj = j + 1
+				}
+
+				vertexB := body.GetShapeVertex(jj)
+
+				raylib.DrawLineV(vertexA, vertexB, raylib.Green) // Draw a line between two vertex positions
+			}
+		}
+
+		raylib.DrawRectangle(0, screenHeight-49, screenWidth, 49, raylib.Black)
+
+		raylib.DrawText("Friction amount", (screenWidth-raylib.MeasureText("Friction amount", 30))/2, 75, 30, raylib.White)
+		raylib.DrawText("0.1", int32(bodyA.Position.X)-raylib.MeasureText("0.1", 20)/2, int32(bodyA.Position.Y)-7, 20, raylib.White)
+		raylib.DrawText("1", int32(bodyB.Position.X)-raylib.MeasureText("1", 20)/2, int32(bodyB.Position.Y)-7, 20, raylib.White)
+
+		raylib.DrawText("Press 'R' to reset example", 10, 10, 10, raylib.White)
+
+		raylib.DrawText("Physac", logoX, logoY, 30, raylib.White)
+		raylib.DrawText("Powered by", logoX+50, logoY-7, 10, raylib.White)
+
+		raylib.EndDrawing()
+	}
+
+	physics.Close() // Unitialize physics
+
+	raylib.CloseWindow()
+}