Add a textured curve example (#2821)

examples/textures/textures_textured_curve.c

@@ -0,0 +1,241 @@
+/*******************************************************************************************
+*
+*   raylib [textures] example - Draw a texture along a segmented curve
+*
+*   Example originally created with raylib 4.5
+*
+*   Example contributed by Jeffery Myers and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2019-2022 Jeffery Myers and Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+
+#include "raylib.h"
+#include "raymath.h"
+#include "rlgl.h"
+
+Texture RoadTexture = { 0 };
+
+bool ShowCurve = false;
+
+float Width = 50;
+int Segments = 24;
+
+Vector2 SP = { 0 };
+Vector2 SPTangent = { 0 };
+
+Vector2 EP = { 0 };
+Vector2 EPTangent = { 0 };
+
+Vector2* Selected = NULL;
+
+void DrawCurve()
+{
+	if (ShowCurve)
+		DrawLineBezierCubic(SP, EP, SPTangent, EPTangent, 2, BLUE);
+
+	// draw the various control points and highlight where the mouse is
+	DrawLineV(SP, SPTangent, SKYBLUE);
+	DrawLineV(EP, EPTangent, PURPLE);
+	Vector2 mouse = GetMousePosition();
+
+	if (CheckCollisionPointCircle(mouse, SP, 6))
+		DrawCircleV(SP, 7, YELLOW);
+	DrawCircleV(SP, 5, RED);
+
+	if (CheckCollisionPointCircle(mouse, SPTangent, 6))
+		DrawCircleV(SPTangent, 7, YELLOW);
+	DrawCircleV(SPTangent, 5, MAROON);
+
+	if (CheckCollisionPointCircle(mouse, EP, 6))
+		DrawCircleV(EP, 7, YELLOW);
+	DrawCircleV(EP, 5, GREEN);
+
+	if (CheckCollisionPointCircle(mouse, EPTangent, 6))
+		DrawCircleV(EPTangent, 7, YELLOW);
+	DrawCircleV(EPTangent, 5, DARKGREEN);
+}
+
+void EditCurve()
+{
+	// if the mouse is not down, we are not editing the curve so clear the selection
+	if (!IsMouseButtonDown(MOUSE_LEFT_BUTTON))
+	{
+		Selected = NULL;
+		return;
+	}
+
+	// if a point was selected, move it
+	if (Selected)
+	{
+		*Selected = Vector2Add(*Selected, GetMouseDelta());
+		return;
+	}
+
+	// the mouse is down, and nothing was selected, so see if anything was picked
+	Vector2 mouse = GetMousePosition();
+
+	if (CheckCollisionPointCircle(mouse, SP, 6))
+		Selected = &SP;
+	else if (CheckCollisionPointCircle(mouse, SPTangent, 6))
+		Selected = &SPTangent;
+	else if (CheckCollisionPointCircle(mouse, EP, 6))
+		Selected = &EP;
+	else if (CheckCollisionPointCircle(mouse, EPTangent, 6))
+		Selected = &EPTangent;
+}
+
+void DrawTexturedCurve()
+{
+	const float step = 1.0f / Segments;
+
+	Vector2 previous = SP;
+	Vector2 previousTangent = { 0 };
+	float previousV = 0;
+
+	// we can't compute a tangent for the first point, so we need to reuse the tangent from the first segment
+	bool tangentSet = false;
+
+	Vector2 current = { 0 };
+	float t = 0.0f;
+
+	for (int i = 1; i <= Segments; i++)
+	{
+		// segment the curve
+		t = step * i;
+		float a = powf(1 - t, 3);
+		float b = 3 * powf(1 - t, 2) * t;
+		float c = 3 * (1 - t) * powf(t, 2);
+		float d = powf(t, 3);
+
+		// compute the endpoint for this segment
+		current.y = a * SP.y + b * SPTangent.y + c * EPTangent.y + d * EP.y;
+		current.x = a * SP.x + b * SPTangent.x + c * EPTangent.x + d * EP.x;
+
+		// vector from previous to current
+		Vector2 delta = { current.x - previous.x, current.y - previous.y };
+
+		// the right hand normal to the delta vector
+		Vector2 normal = Vector2Normalize((Vector2){ -delta.y, delta.x });
+
+		// the v texture coordinate of the segment (add up the length of all the segments so far)
+		float v = previousV + Vector2Length(delta);
+
+		// make sure the start point has a normal
+		if (!tangentSet)
+		{
+			previousTangent = normal;
+			tangentSet = true;
+		}
+
+		// extend out the normals from the previous and current points to get the quad for this segment
+		Vector2 prevPosNormal = Vector2Add(previous, Vector2Scale(previousTangent, Width));
+		Vector2 prevNegNormal = Vector2Add(previous, Vector2Scale(previousTangent, -Width));
+
+		Vector2 currentPosNormal = Vector2Add(current, Vector2Scale(normal, Width));
+		Vector2 currentNegNormal = Vector2Add(current, Vector2Scale(normal, -Width));
+
+		// draw the segment as a quad
+		rlSetTexture(RoadTexture.id);
+		rlBegin(RL_QUADS);
+
+		rlColor4ub(255,255,255,255);
+		rlNormal3f(0.0f, 0.0f, 1.0f);
+
+		rlTexCoord2f(0, previousV);
+		rlVertex2f(prevNegNormal.x, prevNegNormal.y);
+
+		rlTexCoord2f(1, previousV);
+		rlVertex2f(prevPosNormal.x, prevPosNormal.y);
+
+		rlTexCoord2f(1, v);
+		rlVertex2f(currentPosNormal.x, currentPosNormal.y);
+
+		rlTexCoord2f(0, v);
+		rlVertex2f(currentNegNormal.x, currentNegNormal.y);
+
+		rlEnd();
+
+		// the current step is the start of the next step
+		previous = current;
+		previousTangent = normal;
+		previousV = v;
+	}
+}
+
+void UpdateOptions()
+{
+	if (IsKeyPressed(KEY_SPACE))
+		ShowCurve = !ShowCurve;
+
+	// width
+	if (IsKeyPressed(KEY_EQUAL))
+		Width += 2;
+
+	if (IsKeyPressed(KEY_MINUS))
+		Width -= 2;
+
+	if (Width < 2)
+		Width = 2;
+
+	// segments
+
+	if (IsKeyPressed(KEY_LEFT_BRACKET))
+		Segments -= 2;
+
+	if (IsKeyPressed(KEY_RIGHT_BRACKET))
+		Segments += 2;
+
+	if (Segments < 2)
+		Segments = 2;
+}
+
+int main ()
+{
+	// set up the window
+	SetConfigFlags(FLAG_VSYNC_HINT);
+	InitWindow(1280, 800, "raylib [textures] examples - textured curve");
+	SetTargetFPS(144);
+
+	// load the road texture
+	RoadTexture = LoadTexture("resources/roadTexture_01.png");
+
+	// setup the curve
+	SP = (Vector2){ 80, 400 };
+	SPTangent = (Vector2){ 600, 100 };
+
+	EP = (Vector2){ 1200, 400 };
+	EPTangent = (Vector2){ 600, 700 };
+
+	// game loop
+	while (!WindowShouldClose())
+	{
+		EditCurve();
+		UpdateOptions();
+
+		BeginDrawing();
+
+		ClearBackground(BLACK);
+
+		DrawTexturedCurve();
+		DrawCurve();
+	
+		DrawText("Drag points to move curve, press space to show/hide base curve", 10, 0, 20, WHITE);
+		DrawText(TextFormat("Width %2.0f + and - to adjust", Width), 10, 20, 20, WHITE);
+		DrawText(TextFormat("Segments %d [ and ] to adjust", Segments), 10, 40, 20, WHITE);
+		DrawFPS(10, 60);
+
+		EndDrawing();
+	}
+
+	// cleanup
+	UnloadTexture(RoadTexture);
+	CloseWindow();
+	return 0;
+}
+
+