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/*
* Descent 3
* Copyright (C) 2024 Parallax Software
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "3d.h"
#include "HardwareInternal.h"
#include <string.h>
struct InstanceContext {
matrix m_viewMatrix; // matrix
matrix m_unscaledMatrix; // unscaled matrix
vector m_viewPosition; // position
float m_modelView[4][4]; // model/view transform
};
#define MAX_INSTANCE_DEPTH 30
static InstanceContext sInstanceStack[MAX_INSTANCE_DEPTH];
static int sInstanceDepth = 0;
// instance at specified point with specified orientation
void g3_StartInstanceMatrix(vector *pos, matrix *orient) {
ASSERT(orient != NULL);
ASSERT(sInstanceDepth < MAX_INSTANCE_DEPTH);
sInstanceStack[sInstanceDepth].m_viewMatrix = View_matrix;
sInstanceStack[sInstanceDepth].m_viewPosition = View_position;
sInstanceStack[sInstanceDepth].m_unscaledMatrix = Unscaled_matrix;
memcpy(sInstanceStack[sInstanceDepth].m_modelView, gTransformModelView, sizeof(gTransformModelView));
++sInstanceDepth;
// step 1: subtract object position from view position
vector tempv = View_position - *pos;
// step 2: rotate view vector through object matrix
View_position = tempv * *orient;
// step 3: rotate object matrix through view_matrix (vm = ob * vm)
matrix tempm, tempm2 = ~*orient;
tempm = tempm2 * View_matrix;
View_matrix = tempm;
tempm = tempm2 * Unscaled_matrix;
Unscaled_matrix = tempm;
// transform the model/view matrix
g3_GetModelViewMatrix(&View_position, &Unscaled_matrix, (float *)gTransformModelView);
g3_UpdateFullTransform();
}
// instance at specified point with specified orientation
void g3_StartInstanceAngles(vector *pos, angvec *angles) {
if (angles == NULL) {
matrix ident;
vm_MakeIdentity(&ident);
g3_StartInstanceMatrix(pos, &ident);
return;
}
matrix tm;
vm_AnglesToMatrix(&tm, angles->p, angles->h, angles->b);
g3_StartInstanceMatrix(pos, &tm);
}
// pops the old context
void g3_DoneInstance() {
--sInstanceDepth;
ASSERT(sInstanceDepth >= 0);
View_position = sInstanceStack[sInstanceDepth].m_viewPosition;
View_matrix = sInstanceStack[sInstanceDepth].m_viewMatrix;
Unscaled_matrix = sInstanceStack[sInstanceDepth].m_unscaledMatrix;
memcpy(gTransformModelView, sInstanceStack[sInstanceDepth].m_modelView, sizeof(gTransformModelView));
g3_UpdateFullTransform();
}
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