Descent3/renderer/HardwareSetup.cpp

/*
* 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 <cstring>

#include "3d.h"
#include "HardwareInternal.h"
#include "renderer.h"

// User-specified aspect ratio, stored as w/h
static float sAspect = 0.0f;

// allows the user to specify an aspect ratio that overrides the renderer's
// The parameter is the w/h of the screen pixels
void g3_SetAspectRatio(float aspect) { sAspect = aspect; }
// returns the user-specified aspect ratio used to override the renderer's
float g3_GetAspectRatio() { return sAspect; }

void g3_GetViewPortMatrix(float *viewMat) {
  // extract the viewport data from the renderer
  int viewportWidth, viewportHeight;
  int viewportX, viewportY;
  rend_GetProjectionScreenParameters(viewportX, viewportY, viewportWidth, viewportHeight);

  float viewportWidthOverTwo = ((float)viewportWidth) * 0.5f;
  float viewportHeightOverTwo = ((float)viewportHeight) * 0.5f;

  // setup the matrix
  memset(viewMat, 0, sizeof(float) * 16);
  viewMat[0] = viewportWidthOverTwo;
  viewMat[5] = -viewportHeightOverTwo;
  viewMat[12] = viewportWidthOverTwo + (float)viewportX;
  viewMat[13] = viewportHeightOverTwo + (float)viewportY;
  viewMat[10] = viewMat[15] = 1.0f;
}

void g3_GetProjectionMatrix(float zoom, float *projMat) {
  // get window size
  int viewportWidth, viewportHeight;
  rend_GetProjectionParameters(&viewportWidth, &viewportHeight);

  float s = ((float)viewportWidth) / ((float)viewportHeight);
  float vertical_fov = zoom * 3.0f / 4.0f;

  // setup the matrix
  memset(projMat, 0, sizeof(float) * 16);

  // calculate 1/tan(fov)
  float oOT = 1.0f / vertical_fov;

  // fill in the matrix
  // Go read https://www.songho.ca/opengl/gl_projectionmatrix.html
  // if you feel like doing the math again :)
	if (s <= 1.0f)
	{
		projMat[0] = oOT;
		projMat[5] = oOT * s;
	}
	else
	{
		projMat[0] = oOT / s;
		projMat[5] = oOT;
	}

  projMat[10] = 1.0f;
  projMat[11] = 1.0f;
  projMat[14] = -1.0f;
}

// start the frame
void g3_StartFrame(vector *view_pos, matrix *view_matrix, float zoom) {
  // initialize the viewport transform
  g3_GetViewPortMatrix((float *)gTransformViewPort);
  g3_GetProjectionMatrix(zoom, (float *)gTransformProjection);
  g3_GetModelViewMatrix(view_pos, view_matrix, (float *)gTransformModelView);
  g3_UpdateFullTransform();

  // get window size
  rend_GetProjectionParameters(&Window_width, &Window_height);

  // Set vars for projection
  Window_w2 = ((scalar)Window_width) * 0.5f;
  Window_h2 = ((scalar)Window_height) * 0.5f;

  // ISB trick: use the window aspect only, screen aspect ratio
  // is not important because we assume pixels are square
  scalar s = (scalar)Window_height / (scalar)Window_width;

  Matrix_scale = { s <= 1.0f ? s : 1.0f / s, 1.0f };


  //ISB: Convert zoom into vertical FOV for convenience
  zoom *= 3.f / 4.f;

  Matrix_scale.z() = 1.0f;

  // Set the view variables
  View_position = *view_pos;
  View_zoom = zoom;
  Unscaled_matrix = *view_matrix;

  // Scale x and y to zoom in or out;
  float oOZ = 1.0f / View_zoom;
  Matrix_scale.x() = Matrix_scale.x() * oOZ;
  Matrix_scale.y() = Matrix_scale.y() * oOZ;

  // Scale the matrix elements
  View_matrix.rvec = Unscaled_matrix.rvec * Matrix_scale.x();
  View_matrix.uvec = Unscaled_matrix.uvec * Matrix_scale.y();
  View_matrix.fvec = Unscaled_matrix.fvec * Matrix_scale.z();

  // Reset the list of free points
  InitFreePoints();

  // Reset the far clip plane
  g3_ResetFarClipZ();
}

// this doesn't do anything, but is here for completeness
void g3_EndFrame(void) {
  // make sure temp points are free
  CheckTempPoints();
}

// get the current view position
void g3_GetViewPosition(vector *vp) { *vp = View_position; }

void g3_GetViewMatrix(matrix *mat) { *mat = View_matrix; }

void g3_GetUnscaledMatrix(matrix *mat) { *mat = Unscaled_matrix; }

// Gets the matrix scale vector
void g3_GetMatrixScale(vector *matrix_scale) { *matrix_scale = Matrix_scale; }