Torque2D/engine/source/Box2D/Particle/b2Particle.cpp

/*
* Copyright (c) 2013 Google, Inc.
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#include <Box2D/Particle/b2Particle.h>
#include <Box2D/Common/b2Draw.h>

#define B2PARTICLECOLOR_BITS_PER_COMPONENT (sizeof(uint8) << 3)
// Maximum value of a b2ParticleColor component.
#define B2PARTICLECOLOR_MAX_VALUE \
	((1U << B2PARTICLECOLOR_BITS_PER_COMPONENT) - 1)

/// Number of bits used to store each b2ParticleColor component.
const uint8 b2ParticleColor::k_bitsPerComponent =
	B2PARTICLECOLOR_BITS_PER_COMPONENT;
const float32 b2ParticleColor::k_maxValue = (float)B2PARTICLECOLOR_MAX_VALUE;
const float32 b2ParticleColor::k_inverseMaxValue =
	1.0f / (float)B2PARTICLECOLOR_MAX_VALUE;

b2ParticleColor b2ParticleColor_zero(0, 0, 0, 0);

b2ParticleColor::b2ParticleColor(const b2Color& color)
{
	Set(color);
}

b2Color b2ParticleColor::GetColor() const
{
	return b2Color(k_inverseMaxValue * r,
				   k_inverseMaxValue * g,
				   k_inverseMaxValue * b);
}

void b2ParticleColor::Set(const b2Color& color)
{
	Set((uint8)(k_maxValue * color.r),
		(uint8)(k_maxValue * color.g),
		(uint8)(k_maxValue * color.b),
		B2PARTICLECOLOR_MAX_VALUE);
}

int32 b2CalculateParticleIterations(
	float32 gravity, float32 radius, float32 timeStep)
{
	// In some situations you may want more particle iterations than this,
	// but to avoid excessive cycle cost, don't recommend more than this.
	const int32 B2_MAX_RECOMMENDED_PARTICLE_ITERATIONS = 8;
	const float32 B2_RADIUS_THRESHOLD = 0.01f;
	int32 iterations =
		(int32) ceilf(b2Sqrt(gravity / (B2_RADIUS_THRESHOLD * radius)) * timeStep);
	return b2Clamp(iterations, 1, B2_MAX_RECOMMENDED_PARTICLE_ITERATIONS);
}