[rmodels] DrawSphereEx() optimization

[smalltimewizard]

Removed unnecessary cos/sin usage in DrawSphereEx(). For a sphere with 16 rings and 16 slices (as with DrawSphere()), 8640 cos/sin calls pre-optimization are reduced to 72.

Benchmark (1000 spheres):

// gcc main.c -o main.exe -I ./include -L ./lib -lraylib -lgdi32 -lwinmm

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <assert.h>

#include "raylib.h"
#include "raymath.h"

Camera3D camera = {
	.position = (Vector3){-50.0f,50.0f,-50.0f},
	.target = (Vector3){22.5f,22.5f,22.5f},
	.up = (Vector3){0,1,0},
	.fovy = 70.0f,
	.projection = CAMERA_PERSPECTIVE,
};

int main(int argc, char** argv) {
	InitWindow(1280, 720, "DrawSphere benchmark");
	
	int density = 10; // density^3 = number of rendered spheres
	float scale = 50.0f;
	float cameraspeed = 15.0f;
	
	while (!WindowShouldClose()) {
		float deltatime = GetFrameTime();
		printf("%f\n", deltatime);
		
		Vector3 camerafacing = Vector3Normalize(Vector3Subtract(camera.target, camera.position));
		
		if (IsKeyDown(KEY_W)) {
		camera.position = Vector3Add(camera.position, Vector3Scale(camerafacing, cameraspeed*deltatime));
		}
		if (IsKeyDown(KEY_S)) {
			camera.position = Vector3Add(camera.position, Vector3Scale(camerafacing, -cameraspeed*deltatime));
		}
		if (IsKeyDown(KEY_A)) {
			camera.position = Vector3Add(camera.position, Vector3Scale(Vector3Normalize(Vector3CrossProduct(camerafacing, camera.up)), -cameraspeed*deltatime));
		}
		if (IsKeyDown(KEY_D)) {
			camera.position = Vector3Add(camera.position, Vector3Scale(Vector3Normalize(Vector3CrossProduct(camerafacing, camera.up)), cameraspeed*deltatime));
		}
		
		BeginDrawing();
		ClearBackground(RAYWHITE);
			BeginMode3D(camera);
				for (int i = 0; i < density; i++) {
					for (int j = 0; j < density; j++) {
						for (int k = 0; k < density; k++) {
							Color color = (Color){255-i*20, 255-j*20, k*20, 255};
							DrawSphere((Vector3){i*scale/density,j*scale/density,k*scale/density}, 1.0f, color);
						}
					}
				}
			EndMode3D();
			DrawFPS(10,10);
		EndDrawing();
	}
	
	CloseWindow();
	
	return 0;
};

I compiled raylib (mingw-w64, static, Release) without and with the optimization. On my machine, the above benchmark gives a 75 ms frametime without, 50 ms with the optimization.

[smalltimewizard]

I have another version without calloc/free, but it's not faster (than the calloc version) on my machine. If someone wants to play around with it:

// Draw sphere with extended parameters
void DrawSphereEx(Vector3 centerPos, float radius, int rings, int slices, Color color)
{
    rlPushMatrix();
        // NOTE: Transformation is applied in inverse order (scale -> translate)
        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
        rlScalef(radius, radius, radius);

        rlBegin(RL_TRIANGLES);
            rlColor4ub(color.r, color.g, color.b, color.a);

            float cosring[2];
            float sinring[2];
            float cosslice[2];
            float sinslice[2];
            cosring[1] = 1.0f;
            sinring[1] = 0.0f;
            cosslice[1] = 1.0f;
            sinslice[1] = 0.0f;

            for (int i = 0; i < (rings + 2); i++)
            {
                float nextringangle = DEG2RAD*(270 + (180.0f/(rings + 1))*(i+1));
                cosring[0] = cosring[1];
                sinring[0] = sinring[1];
                cosring[1] = cosf(nextringangle);
                sinring[1] = sinf(nextringangle);

                for (int j = 0; j < slices; j++)
                {
                    float nextsliceangle = DEG2RAD*(360.0f*(j+1)/slices);
                    cosslice[0] = cosslice[1];
                    sinslice[0] = sinslice[1];
                    cosslice[1] = cosf(nextsliceangle);
                    sinslice[1] = sinf(nextsliceangle);

                    rlVertex3f(cosring[0]*sinslice[0], sinring[0], cosring[0]*cosslice[0]);
                    rlVertex3f(cosring[1]*sinslice[1], sinring[1], cosring[1]*cosslice[1]);
                    rlVertex3f(cosring[1]*sinslice[0], sinring[1], cosring[1]*cosslice[0]);

                    rlVertex3f(cosring[0]*sinslice[0], sinring[0], cosring[0]*cosslice[0]);
                    rlVertex3f(cosring[0]*sinslice[1], sinring[0], cosring[0]*cosslice[1]);
                    rlVertex3f(cosring[1]*sinslice[1], sinring[1], cosring[1]*cosslice[1]);
                }
            }

        rlEnd();
    rlPopMatrix();
}

[raysan5]

@smalltimewizard I'd prefer to avoid allocators inside the function, what is the improvement wihtout the allocators in comparison to original version?

[smalltimewizard]

I get 65 ms frametime from my benchmark with no allocators (for a sphere with 16 rings and 16 slices, the no allocators algorithm makes 612 cos/sin calls).
I also have an idea for a better algorithm, but not sure when I will find time to work on it.

[raysan5]

@smalltimewizard I'm reviewing those numbers and they seem irregularly big, are we talking about milliseconds or nanoseconds?

In any case, I'm considering if this change really worth it because I adds an extra level of code complexity for newcomers and readibility for future maintenance, for the performance benefit it provides.

EDIT: I see those numbers are computed for 1000 spheres, what is exactly computed? A for loop calling this function 1000 times? I think it should be measured just the function body 1 time for more accurate numbers (or 1 function call).

[smalltimewizard]

New barebones benchmark:

// gcc main.c -o main.exe -I "./include" -L "./lib" -lraylib -lgdi32 -lwinmm

#include <stdio.h>
#include <time.h>

#include "raylib.h"
#include "raymath.h"

#define RUNS 1000

Camera3D camera = {
	.position = (Vector3){0,3,0},
	.target = (Vector3){0,0,100},
	.up = (Vector3){0,1,0},
	.fovy = 70.0f,
	.projection = CAMERA_PERSPECTIVE,
};

int main(int argc, char** argv) {
	InitWindow(1280, 720, "DrawSphere benchmark");
	
	while (!WindowShouldClose()) {
		BeginDrawing();
			ClearBackground(RAYWHITE);
			BeginMode3D(camera);
				double timerstart = (double) clock();
				for (int i = 0; i < RUNS; i++) {
					DrawSphereEx((Vector3){0,0,i}, 1.0f, 16, 16, RED);
				}
				printf("%d calls of DrawSphere() took %f seconds.\n", RUNS, (double) (clock()-timerstart)/CLOCKS_PER_SEC);
			EndMode3D();
			DrawFPS(10,10);
		EndDrawing();
	}
	
	CloseWindow();
	
	return 0;
};

On my machine (mingw-w64, compiled as Release, static library) for 1000 DrawSphereEx() calls:
The original algorithm completes in 0.074 seconds and with 32 rings/slices completes in 0.33 seconds.
The heap allocation algorithm completes in 0.055 seconds and with 32 rings/slices completes in 0.21 seconds.
The stack allocation algorithm completes in 0.063 seconds and with 32 rings/slices completes in 0.24 seconds.

[smalltimewizard]

@raysan5 Rebuilt DrawSphereEx from scratch -- the new one uses stack allocation and is hopefully simple enough.
It gives 1000 spheres in 0.048 seconds and 1000 spheres of 32 rings/slices in 0.181 seconds.
(And just to flex, it makes only 4 cos/sin calls. :P)

[raysan5]

@smalltimewizard Thanks for the improvement! I'm merging it but I will also keep the original one for educational pouposes