70 lines
2.5 KiB
C
70 lines
2.5 KiB
C
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/*
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** Copyright 1991, 1992, 1993, Silicon Graphics, Inc.
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** All Rights Reserved.
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**
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** This is UNPUBLISHED PROPRIETARY SOURCE CODE of Silicon Graphics, Inc.;
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** the contents of this file may not be disclosed to third parties, copied or
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** duplicated in any form, in whole or in part, without the prior written
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** permission of Silicon Graphics, Inc.
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**
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** RESTRICTED RIGHTS LEGEND:
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** Use, duplication or disclosure by the Government is subject to restrictions
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** as set forth in subdivision (c)(1)(ii) of the Rights in Technical Data
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** and Computer Software clause at DFARS 252.227-7013, and/or in similar or
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** successor clauses in the FAR, DOD or NASA FAR Supplement. Unpublished -
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** rights reserved under the Copyright Laws of the United States.
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*/
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#include "precomp.h"
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#pragma hdrstop
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/*
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** Initialize a lookup table that is indexed by the iterated alpha value.
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** The table indicates whether the alpha test passed or failed, based on
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** the current alpha function and the alpha reference value.
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**
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** NOTE: The alpha span routines will never be called if the alpha test
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** is GL_ALWAYS (its useless) or if the alpha test is GL_NEVER. This
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** is accomplished in the __glGenericPickSpanProcs procedure.
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*/
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void FASTCALL __glValidateAlphaTest(__GLcontext *gc)
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{
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GLubyte *atft;
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GLint i, limit;
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GLint ref;
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GLenum alphaTestFunc = gc->state.raster.alphaFunction;
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limit = gc->constants.alphaTestSize;
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ref = (GLint)
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((gc->state.raster.alphaReference * gc->frontBuffer.alphaScale) *
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gc->constants.alphaTableConv);
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/*
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** Allocate alpha test function table the first time. It needs
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** to have at most one entry for each possible alpha value.
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*/
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atft = gc->frontBuffer.alphaTestFuncTable;
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if (!atft) {
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atft = (GLubyte*)
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(*gc->imports.malloc)(gc, (size_t) ((limit) * sizeof(GLubyte)));
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gc->frontBuffer.alphaTestFuncTable = atft;
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}
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/*
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** Build up alpha test lookup table. The computed alpha value is
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** used as an index into this table to determine if the alpha
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** test passed or failed.
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*/
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for (i = 0; i < limit; i++) {
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switch (alphaTestFunc) {
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case GL_NEVER: *atft++ = GL_FALSE; break;
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case GL_LESS: *atft++ = (GLubyte) (i < ref); break;
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case GL_EQUAL: *atft++ = (GLubyte) (i == ref); break;
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case GL_LEQUAL: *atft++ = (GLubyte) (i <= ref); break;
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case GL_GREATER: *atft++ = (GLubyte) (i > ref); break;
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case GL_NOTEQUAL: *atft++ = (GLubyte) (i != ref); break;
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case GL_GEQUAL: *atft++ = (GLubyte) (i >= ref); break;
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case GL_ALWAYS: *atft++ = GL_TRUE; break;
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}
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}
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}
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