mirror of https://github.com/skeeto/pixelcity.git
134 lines
4.1 KiB
C++
134 lines
4.1 KiB
C++
/*-----------------------------------------------------------------------------
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Visible.cpp
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2009 Shamus Young
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-------------------------------------------------------------------------------
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This module runs the visibility grid, a 2-dimensional array that aids in
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culling objects during rendering.
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There are many ways this could be refined or sped up, although tests indicate
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it's not a huge drain on performance.
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-----------------------------------------------------------------------------*/
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#include <windows.h>
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#include <math.h>
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#include "glTypes.h"
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#include "camera.h"
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#include "macro.h"
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#include "math.h"
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#include "visible.h"
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#include "world.h"
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#include "win.h"
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static bool vis_grid[GRID_SIZE][GRID_SIZE];
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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bool Visible (GLvector pos)
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{
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return vis_grid[WORLD_TO_GRID(pos.x)][WORLD_TO_GRID(pos.z)];
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}
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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bool Visible (int x, int z)
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{
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return vis_grid[x][z];
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}
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/*-----------------------------------------------------------------------------
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-----------------------------------------------------------------------------*/
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void VisibleUpdate (void)
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{
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GLvector angle;
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GLvector position;
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int x, y, grid_x, grid_z;
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int left, right, front, back;
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float angle_to;
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float angle_diff;
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float target_x, target_z;
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LIMIT_INTERVAL (10);
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//Clear the visibility table
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ZeroMemory (vis_grid, sizeof (vis_grid));
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//Calculate which cell the camera is in
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angle = CameraAngle ();
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position = CameraPosition ();
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grid_x = WORLD_TO_GRID(position.x);
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grid_z = WORLD_TO_GRID(position.z);
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//Cells directly adjactent to the camera might technically fall out of the fov,
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//but still have a few objects poking into screenspace when looking up or down.
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//Rather than obsess over sorting those objects properly, it's more efficient to
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//just mark them visible.
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left = right = front = back = 3;
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//Looking north, can't see south.
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if (angle.y < 45.0f || angle.y > 315.0f)
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front = 0;
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//Looking south, can't see north
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if (angle.y > 135.0f && angle.y < 225.0f)
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back = 0;
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//Looking east, can't see west
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if (angle.y > 45.0f && angle.y < 135.0f)
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left = 0;
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//Looking west, can't see east
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if (angle.y > 225.0f && angle.y < 315.0f)
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right = 0;
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//Now mark the block around us the might be visible
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for (x = grid_x - left; x <= grid_x + right; x++) {
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if (x < 0 || x >= GRID_SIZE) //just in case the camera leaves the world map
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continue;
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for (y = grid_z - back; y <= grid_z + front; y++) {
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if (y < 0 || y >= GRID_SIZE) //just in case the camera leaves the world map
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continue;
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vis_grid[x][y] = true;
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}
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}
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//Doesn't matter where we are facing, objects in current cell are always visible
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vis_grid[grid_x][grid_z] = true;
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//Here, we look at the angle from the current camera position to the cell
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//on the grid, and how much that angle deviates from the current view angle.
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for (x = 0; x < GRID_SIZE; x++) {
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for (y = 0; y < GRID_SIZE; y++) {
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//if we marked it visible earlier, skip all this math
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if (vis_grid[x][y])
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continue;
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//if the camera is to the left of this cell, use the left edge
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if (grid_x < x)
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target_x = (float)x * GRID_RESOLUTION;
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else
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target_x = (float)(x + 1) * GRID_RESOLUTION;
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if (grid_z < y)
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target_z = (float)y * GRID_RESOLUTION;
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else
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target_z = (float)(y + 1) * GRID_RESOLUTION;
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angle_to = 180 - MathAngle (target_x, target_z, position.x, position.z);
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//Store how many degrees the cell is to the
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angle_diff = (float)fabs (MathAngleDifference (angle.y, angle_to));
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vis_grid[x][y] = angle_diff < 45;
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}
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}
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}
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