update_position.cg

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#include "sph.cg"

void main(fixed index : TEXCOORD0,
		  uniform samplerRECT attr_rect : TEXUNIT0,
		  uniform float timestep,
		  out float3 result : COLOR)
{
	float3 pos = f3texRECT(attr_rect, half2(index, GPU_ATTR_PUSHPOS));
	float3 vel = f3texRECT(attr_rect, half2(index,  GPU_ATTR_VEL));
	float3 acc = f3texRECT(attr_rect, half2(index, GPU_ATTR_ACC));
	//float3 exacc = f3texRECT(attr_rect, float2(index, GPU_ATTR_EXACC));
	float3 gravity = float3(0.0, 0.0, -9.8);

	float3 new_v = vel + timestep*(acc  + gravity - 1.1f*vel);

	//float3 mid_v = 0.5f*(vel + new_v);
	 
	//if (length(mid_v) < 0.06f)
	//	result = pos;
//	else result = pos + 0.5f*timestep*(vel + new_v);
	result = pos + 0.5f*timestep*(vel + new_v);
}