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118 lines
3.6 KiB
C++
118 lines
3.6 KiB
C++
/*
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** SSA barycentric weight and viewport calculations
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** Copyright (c) 2016 Magnus Norddahl
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**
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** This software is provided 'as-is', without any express or implied
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** warranty. In no event will the authors be held liable for any damages
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** arising from the use of this software.
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**
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** Permission is granted to anyone to use this software for any purpose,
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** including commercial applications, and to alter it and redistribute it
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** freely, subject to the following restrictions:
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**
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** 1. The origin of this software must not be misrepresented; you must not
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** claim that you wrote the original software. If you use this software
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** in a product, an acknowledgment in the product documentation would be
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** appreciated but is not required.
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** 2. Altered source versions must be plainly marked as such, and must not be
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** misrepresented as being the original software.
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** 3. This notice may not be removed or altered from any source distribution.
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**
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*/
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#pragma once
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#include "ssa_vec4f.h"
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#include "ssa_float.h"
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#include "ssa_int.h"
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class SSAViewport
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{
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public:
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SSAViewport(SSAInt x, SSAInt y, SSAInt width, SSAInt height)
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: x(x), y(y), width(width), height(height), right(x + width), bottom(y + height),
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half_width(SSAFloat(width) * 0.5f), half_height(SSAFloat(height) * 0.5f),
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rcp_half_width(1.0f / (SSAFloat(width) * 0.5f)),
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rcp_half_height(1.0f / (SSAFloat(height) * 0.5f))
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{
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}
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SSAInt x, y;
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SSAInt width, height;
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SSAInt right, bottom;
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SSAFloat half_width;
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SSAFloat half_height;
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SSAFloat rcp_half_width;
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SSAFloat rcp_half_height;
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SSAVec4f clip_to_window(SSAVec4f clip) const
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{
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SSAFloat w = clip[3];
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SSAVec4f normalized = SSAVec4f::insert_element(clip / SSAVec4f::shuffle(clip, 3, 3, 3, 3), w, 3);
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return normalized_to_window(normalized);
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}
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SSAVec4f normalized_to_window(SSAVec4f normalized) const
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{
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return SSAVec4f(
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SSAFloat(x) + (normalized[0] + 1.0f) * half_width,
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SSAFloat(y) + (normalized[1] + 1.0f) * half_height,
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0.0f - normalized[2],
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normalized[3]);
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}
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};
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class SSABarycentricWeight
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{
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public:
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SSABarycentricWeight(SSAViewport vp, SSAVec4f v1, SSAVec4f v2);
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SSAFloat from_window_x(SSAInt x) const;
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SSAFloat from_window_y(SSAInt y) const;
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SSAViewport viewport;
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SSAVec4f v1;
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SSAVec4f v2;
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};
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inline SSABarycentricWeight::SSABarycentricWeight(SSAViewport viewport, SSAVec4f v1, SSAVec4f v2)
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: viewport(viewport), v1(v1), v2(v2)
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{
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}
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inline SSAFloat SSABarycentricWeight::from_window_x(SSAInt x) const
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{
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/* SSAFloat xnormalized = (x + 0.5f - viewport.x) * viewport.rcp_half_width - 1.0f;
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SSAFloat dx = v2.x-v1.x;
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SSAFloat dw = v2.w-v1.w;
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SSAFloat a = (v2.x - xnormalized * v2.w) / (dx - xnormalized * dw);
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return a;*/
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SSAFloat xnormalized = (SSAFloat(x) + 0.5f - SSAFloat(viewport.x)) * viewport.rcp_half_width - 1.0f;
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SSAFloat dx = v2[0]-v1[0];
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SSAFloat dw = v2[3]-v1[3];
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SSAFloat t = (xnormalized * v1[3] - v1[0]) / (dx - xnormalized * dw);
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return 1.0f - t;
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}
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inline SSAFloat SSABarycentricWeight::from_window_y(SSAInt y) const
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{
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/* SSAFloat ynormalized = (y + 0.5f - viewport.y) * viewport.rcp_half_height - 1.0f;
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SSAFloat dy = v2.y-v1.y;
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SSAFloat dw = v2.w-v1.w;
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SSAFloat a = (v2.y - ynormalized * v2.w) / (dy - ynormalized * dw);
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return a;*/
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SSAFloat ynormalized = (SSAFloat(y) + 0.5f - SSAFloat(viewport.y)) * viewport.rcp_half_height - 1.0f;
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SSAFloat dy = v2[1]-v1[1];
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SSAFloat dw = v2[3]-v1[3];
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SSAFloat t = (ynormalized * v1[3] - v1[1]) / (dy - ynormalized * dw);
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return 1.0f - t;
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}
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/*
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y = (v1.y + t * dy) / (v1.w + t * dw)
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y * v1.w + y * t * dw = v1.y + t * dy
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y * v1.w - v1.y = t * (dy - y * dw)
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t = (y * v1.w - v1.y) / (dy - y * dw)
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*/
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