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// Decal construction and drawing
// Copyright (C) 2002 David Rosen
// Copyright (C) 2003 Steven Fuller
// Copyright (C) 2023 Nguyễn Gia Phong
//
// This file is part of Black Shades.
//
// Black Shades 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.
//
// Black Shades 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 Black Shades. If not, see <https://www.gnu.org/licenses/>.
const Child = std.meta.Child;
const Model = model.Model;
const XYZ = geom.XYZ;
const assert = std.debug.assert;
const c = @import("cimport.zig");
const geom = @import("geom.zig");
const model = @import("model.zig");
const norm = geom.norm;
const segCrossModelTrans = model.segCrossModelTrans;
const segCrossTrigon = geom.segCrossTrigon;
const splat = geom.splat;
const std = @import("std");
const ones: @Vector(3, f32) = @splat(1.0);
const max_len = 120;
const Kind = enum(c_int) { bullet_hole, crater, blood_pool };
const Decals = extern struct {
// GLuint is always 32-bit.
hole_textures: [2]u32,
blood_textures: [11]u32,
len: u32,
kind: [max_len]Kind,
points: [max_len * 8]XYZ,
numpoints: [max_len]u32,
texcoordsx: [max_len * 8]f32,
texcoordsy: [max_len * 8]f32,
alive: [max_len]f32,
};
fn cross(u: @Vector(3, f32), v: @Vector(3, f32)) @Vector(3, f32) {
return .{
u[1] * v[2] - u[2] * v[1],
u[2] * v[0] - u[0] * v[2],
u[0] * v[1] - u[1] * v[0],
};
}
fn normalize(vector: anytype, unit: Child(@TypeOf(vector))) @TypeOf(vector) {
const d = norm(vector) / unit;
if (d == 0) return vector;
return vector / @as(@TypeOf(vector), @splat(d));
}
fn pointTouchModel(p: @Vector(3, f32), n: @Vector(3, f32),
m: *const Model, move: XYZ, rot: f32) bool {
var temp: XYZ = undefined;
return segCrossModelTrans(@bitCast(p + n), @bitCast(p - n),
m, move, rot, &temp) > -1;
}
export fn addDecal(d: *Decals, kind: Kind, location: XYZ,
size: f32, normal: XYZ, poly: c_int,
m: *const Model, move: XYZ, rot: f32) void {
if (d.len >= max_len) return;
const n: @Vector(3, f32) = @bitCast(normal);
const abs_n = @fabs(n);
var major: u2 = 0;
if (abs_n[1] > abs_n[major])
major = 1;
if (abs_n[2] > abs_n[major])
major = 2;
const r: @Vector(3, f32) = if (@reduce(.And, abs_n != ones))
cross(switch (major) {
0 => .{ 1.0, 0.0, 0.0 },
1 => .{ 0.0, 1.0, 0.0 },
2 => .{ 0.0, 0.0, 1.0 },
else => unreachable,
}, n)
else if (major == 0 and normal.x > 0 or major == 1)
.{ 0.0, 0.0, -1.0 }
else if (major == 0)
.{ 0.0, 0.0, 1.0 }
else
.{ normal.z, 0.0, 0.0 };
const up = normalize(cross(n, r), size / 3.0);
const right = normalize(r, size / 3.0);
const loc: @Vector(3, f32) = @bitCast(location);
const face = m.faces[@intCast(poly)];
const n_eps = n * splat(3, @as(f32, 0.02));
const n_eps2 = n * splat(3, @as(f32, 0.04));
d.kind[d.len] = kind;
d.numpoints[d.len] = 0;
d.alive[d.len] = 0;
for ([_]f32{ -1, 1, 1, -1 }, [_]f32{ -1, -1, 1, 1 }) |x, y| {
var p = loc + right * splat(3, x) + up * splat(3, y);
var i = d.len * 8 + d.numpoints[d.len];
var temp: XYZ = undefined;
if (move.x == 0 and move.y == 0 and move.z == 0 and rot == 0
or segCrossTrigon(@bitCast(p + n_eps2), @bitCast(p - n_eps2),
&face[0].position, &face[1].position,
&face[2].position, &normal, &temp)) {
d.texcoordsx[i] = x * 0.5 + 0.5;
d.texcoordsy[i] = y * 0.5 + 0.5;
d.points[i] = @bitCast(p + n_eps);
d.numpoints[d.len] += 1;
continue;
}
const count_inc = @max(0.01, @min(1.0 / size, 0.2));
var good: bool = false;
var count = 1.0 - count_inc;
while (!good and count > -1.0) : (count -= count_inc) {
d.texcoordsx[i] = x * 0.5 + 0.5;
d.texcoordsy[i] = y * count * 0.5 + 0.5;
p = loc + right * splat(3, x) + up * splat(3, y * count);
good = pointTouchModel(p, n_eps2, m, move, rot);
}
if (good) {
d.points[i] = @bitCast(p + n_eps);
d.numpoints[d.len] += 1;
i += 1;
}
good = false;
count = 1.0 - count_inc;
while (!good and count > -1.0) : (count -= count_inc) {
d.texcoordsx[i] = x * count * 0.5 + 0.5;
d.texcoordsy[i] = y * 0.5 + 0.5;
p = loc + right * splat(3, x * count) + up * splat(3, y);
good = pointTouchModel(p, n_eps2, m, move, rot);
}
if (good) {
d.points[i] = @bitCast(p + n_eps);
d.numpoints[d.len] += 1;
continue;
}
var count2 = 1.0 - count_inc;
while (!good and count2 > -1.0) : (count2 -= count_inc) {
count = 1.0 - count_inc;
while (!good and count > -1.0) : (count -= count_inc) {
d.texcoordsx[i] = x * count2 * 0.5 + 0.5;
d.texcoordsy[i] = y * count * 0.5 + 0.5;
p = loc + right * splat(3, x * count2)
+ up * splat(3, y * count);
good = pointTouchModel(p, n_eps2, m, move, rot);
}
}
if (good) {
d.points[i] = @bitCast(p + n_eps);
d.numpoints[d.len] += 1;
}
}
d.len += 1;
}
export fn drawDecals(d: *const Decals) void {
c.glAlphaFunc(c.GL_GREATER, 0.01);
c.glDepthFunc(c.GL_LEQUAL);
c.glEnable(c.GL_BLEND);
c.glEnable(c.GL_CULL_FACE);
c.glEnable(c.GL_TEXTURE_2D);
c.glEnable(c.GL_LIGHTING);
c.glDepthMask(0);
c.glAlphaFunc(c.GL_GREATER, 0.01);
c.glTexParameterf(c.GL_TEXTURE_2D, c.GL_TEXTURE_WRAP_S, c.GL_CLAMP);
c.glTexParameterf(c.GL_TEXTURE_2D, c.GL_TEXTURE_WRAP_T, c.GL_CLAMP);
c.glBlendFunc(c.GL_SRC_ALPHA, c.GL_ONE_MINUS_SRC_ALPHA);
c.glEnable(c.GL_POLYGON_OFFSET_FILL);
for (0..d.len) |i| {
switch (d.kind[i]) {
.bullet_hole, .crater => |k| {
c.glColor4f(1.0, 1.0, 1.0, 1.0 - d.alive[i] / 10.0);
c.glBindTexture(c.GL_TEXTURE_2D, d.hole_textures[switch (k) {
.bullet_hole => 0,
.crater => 1,
// https://github.com/ziglang/zig/issues/12863
else => unreachable, // TODO: remove
}]);
},
.blood_pool => {
const alpha = if (d.alive[i] < 2.0)
@mod(d.alive[i], 0.2) + 0.8
else
(20.0 - d.alive[i]) / 18.0;
c.glColor4f(1.0, 1.0, 1.0, alpha);
const j: usize = @intFromFloat(d.alive[i] * 5.0);
c.glBindTexture(c.GL_TEXTURE_2D, d.blood_textures[@min(j, 10)]);
},
}
c.glPushMatrix();
c.glBegin(c.GL_TRIANGLE_FAN);
for (0..d.numpoints[i]) |j| {
c.glTexCoord2f(d.texcoordsx[i * 8 + j], d.texcoordsy[i * 8 + j]);
c.glVertex3f(d.points[i * 8 + j].x,
d.points[i * 8 + j].y, d.points[i * 8 + j].z);
}
c.glEnd();
c.glPopMatrix();
}
c.glDepthMask(1);
c.glDisable(c.GL_TEXTURE_2D);
c.glEnable(c.GL_CULL_FACE);
c.glDisable(c.GL_POLYGON_OFFSET_FILL);
c.glDepthFunc(c.GL_LEQUAL);
}
export fn updateDecals(d: *Decals) void {
for (0..d.len) |i| {
d.alive[i] += c.multiplier;
if (d.alive[i] < @as(f32, switch (d.kind[i]) {
.bullet_hole, .crater => 10.0,
.blood_pool => 20.0,
})) continue;
d.len -= 1;
const last = d.len;
d.numpoints[i] = d.numpoints[last];
d.alive[i] = d.alive[last];
d.kind[i] = d.kind[last];
for (0..d.numpoints[i]) |j| {
d.points[i * 8 + j] = d.points[last * 8 + j];
d.texcoordsx[i * 8 + j] = d.texcoordsx[last * 8 + j];
d.texcoordsy[i * 8 + j] = d.texcoordsy[last * 8 + j];
}
}
}
export fn destroyDecals(d: *const Decals) void {
c.glDeleteTextures(2, &d.hole_textures);
c.glDeleteTextures(11, &d.blood_textures);
}
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