qzdoom/tools/drawergen/ssa/ssa_barycentric_weight.h

119 lines
3.6 KiB
C
Raw Normal View History

2016-11-01 20:44:33 +00:00
/*
** SSA barycentric weight and viewport calculations
** Copyright (c) 2016 Magnus Norddahl
**
** 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.
**
*/
#pragma once
#include "ssa_vec4f.h"
#include "ssa_float.h"
#include "ssa_int.h"
class SSAViewport
{
public:
SSAViewport(SSAInt x, SSAInt y, SSAInt width, SSAInt height)
: x(x), y(y), width(width), height(height), right(x + width), bottom(y + height),
half_width(SSAFloat(width) * 0.5f), half_height(SSAFloat(height) * 0.5f),
rcp_half_width(1.0f / (SSAFloat(width) * 0.5f)),
rcp_half_height(1.0f / (SSAFloat(height) * 0.5f))
{
}
SSAInt x, y;
SSAInt width, height;
SSAInt right, bottom;
SSAFloat half_width;
SSAFloat half_height;
SSAFloat rcp_half_width;
SSAFloat rcp_half_height;
SSAVec4f clip_to_window(SSAVec4f clip) const
{
SSAFloat w = clip[3];
SSAVec4f normalized = SSAVec4f::insert_element(clip / SSAVec4f::shuffle(clip, 3, 3, 3, 3), w, 3);
return normalized_to_window(normalized);
}
SSAVec4f normalized_to_window(SSAVec4f normalized) const
{
return SSAVec4f(
SSAFloat(x) + (normalized[0] + 1.0f) * half_width,
SSAFloat(y) + (normalized[1] + 1.0f) * half_height,
0.0f - normalized[2],
normalized[3]);
}
};
class SSABarycentricWeight
{
public:
SSABarycentricWeight(SSAViewport vp, SSAVec4f v1, SSAVec4f v2);
SSAFloat from_window_x(SSAInt x) const;
SSAFloat from_window_y(SSAInt y) const;
SSAViewport viewport;
SSAVec4f v1;
SSAVec4f v2;
};
inline SSABarycentricWeight::SSABarycentricWeight(SSAViewport viewport, SSAVec4f v1, SSAVec4f v2)
: viewport(viewport), v1(v1), v2(v2)
{
}
inline SSAFloat SSABarycentricWeight::from_window_x(SSAInt x) const
{
/* SSAFloat xnormalized = (x + 0.5f - viewport.x) * viewport.rcp_half_width - 1.0f;
SSAFloat dx = v2.x-v1.x;
SSAFloat dw = v2.w-v1.w;
SSAFloat a = (v2.x - xnormalized * v2.w) / (dx - xnormalized * dw);
return a;*/
SSAFloat xnormalized = (SSAFloat(x) + 0.5f - SSAFloat(viewport.x)) * viewport.rcp_half_width - 1.0f;
SSAFloat dx = v2[0]-v1[0];
SSAFloat dw = v2[3]-v1[3];
SSAFloat t = (xnormalized * v1[3] - v1[0]) / (dx - xnormalized * dw);
return 1.0f - t;
}
inline SSAFloat SSABarycentricWeight::from_window_y(SSAInt y) const
{
/* SSAFloat ynormalized = (y + 0.5f - viewport.y) * viewport.rcp_half_height - 1.0f;
SSAFloat dy = v2.y-v1.y;
SSAFloat dw = v2.w-v1.w;
SSAFloat a = (v2.y - ynormalized * v2.w) / (dy - ynormalized * dw);
return a;*/
SSAFloat ynormalized = (SSAFloat(y) + 0.5f - SSAFloat(viewport.y)) * viewport.rcp_half_height - 1.0f;
SSAFloat dy = v2[1]-v1[1];
SSAFloat dw = v2[3]-v1[3];
SSAFloat t = (ynormalized * v1[3] - v1[1]) / (dy - ynormalized * dw);
return 1.0f - t;
}
/*
y = (v1.y + t * dy) / (v1.w + t * dw)
y * v1.w + y * t * dw = v1.y + t * dy
y * v1.w - v1.y = t * (dy - y * dw)
t = (y * v1.w - v1.y) / (dy - y * dw)
*/