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graphics/tinygl/fog.cpp

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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 "graphics/tinygl/zgl.h"
+
+namespace TinyGL {
+
+void GLContext::glopFog(GLParam *p) {
+	int pname = p[1].i;
+
+	switch (pname) {
+	case TGL_FOG_MODE:
+		switch (p[2].i) {
+		case TGL_LINEAR:
+		case TGL_EXP:
+		case TGL_EXP2:
+			fog_mode = p[2].i;
+			break;
+		default:
+			error("tglFog: unknown fog mode");
+			return;
+		}
+		break;
+	case TGL_FOG_DENSITY:
+		if (p[2].f < 0.0f) {
+			error("tglFog: fog density negate param");
+			return;
+		}
+		fog_density = p[2].f;
+		break;
+	case TGL_FOG_START:
+		fog_start = p[2].f;
+		break;
+	case TGL_FOG_END:
+		fog_end = p[2].f;
+		break;
+	case TGL_FOG_COLOR:
+		fog_color = Vector4(clampf(p[2].f, 0.0f, 1.0f),
+		                    clampf(p[3].f, 0.0f, 1.0f),
+		                    clampf(p[4].f, 0.0f, 1.0f),
+		                    clampf(p[5].f, 0.0f, 1.0f));
+		break;
+	default:
+		error("tglFog: param not implemented");
+		return;
+	}
+}
+
+void GLContext::gl_calc_fog_factor(GLVertex *v) {
+	float eye_distance = sqrtf(v->ec.X * v->ec.X + v->ec.Y * v->ec.Y + v->ec.Z * v->ec.Z);
+
+	switch (fog_mode) {
+	case TGL_LINEAR: {
+		float fog_distance = 1.0f;
+		if (fog_start != fog_end)
+			fog_distance /= (fog_end - fog_start);
+		v->fog_factor = (fog_end - eye_distance) * fog_distance;
+		}
+		break;
+	case TGL_EXP:
+		v->fog_factor = expf(-fog_density * eye_distance);
+		break;
+	case TGL_EXP2:
+		v->fog_factor = expf(-(fog_density * fog_density * eye_distance * eye_distance));
+		break;
+	default:
+		v->fog_factor = 0;
+		break;
+	}
+
+	v->fog_factor = clampf(v->fog_factor, 0.0f, 1.0f);
+}
+
+} // end of namespace TinyGL