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◆ main openmsx / src / video / GLSnow.cc
3.0 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#include "GLSnow.hh"
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#include "Display.hh"
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#include "GLContext.hh"
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#include "gl_mat.hh"
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#include "gl_vec.hh"
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#include "random.hh"
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#include <algorithm>
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using namespace gl;
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namespace openmsx {
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GLSnow::GLSnow(Display& display_)
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	: Layer(Coverage::FULL, ZIndex::BACKGROUND)
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	, display(display_)
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	, noiseTexture(true, true) // enable interpolation + wrapping
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{
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	// Create noise texture.
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	auto& generator = global_urng(); // fast (non-cryptographic) random numbers
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	std::uniform_int_distribution distribution(0, 255);
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	std::array<uint8_t, 128 * 128> buf;
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	std::ranges::generate(buf, [&] { return distribution(generator); });
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#if OPENGL_VERSION < OPENGL_3_3
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	glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, 128, 128, 0,
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	             GL_LUMINANCE, GL_UNSIGNED_BYTE, buf.data());
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#else
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	// GL_LUMINANCE no longer supported in newer versions
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	glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, 128, 128, 0,
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	             GL_RED, GL_UNSIGNED_BYTE, buf.data());
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	GLint swizzleMask[] = {GL_RED, GL_RED, GL_RED, GL_ONE};
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	glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_RGBA, swizzleMask);
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#endif
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	static constexpr std::array pos = {
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		std::array{vec2{-1, -1}, vec2{ 1, -1}, vec2{ 1,  1}, vec2{-1,  1}},
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		std::array{vec2{-1,  1}, vec2{ 1,  1}, vec2{ 1, -1}, vec2{-1, -1}},
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		std::array{vec2{-1,  1}, vec2{-1, -1}, vec2{ 1, -1}, vec2{ 1,  1}},
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		std::array{vec2{ 1,  1}, vec2{ 1, -1}, vec2{-1, -1}, vec2{-1,  1}},
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		std::array{vec2{ 1,  1}, vec2{-1,  1}, vec2{-1, -1}, vec2{ 1, -1}},
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		std::array{vec2{ 1, -1}, vec2{-1, -1}, vec2{-1,  1}, vec2{ 1,  1}},
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		std::array{vec2{ 1, -1}, vec2{ 1,  1}, vec2{-1,  1}, vec2{-1, -1}},
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		std::array{vec2{-1, -1}, vec2{-1,  1}, vec2{ 1,  1}, vec2{ 1, -1}},
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	};
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	glBindBuffer(GL_ARRAY_BUFFER, vbo[0].get());
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	glBufferData(GL_ARRAY_BUFFER, sizeof(pos), pos.data(), GL_STATIC_DRAW);
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	glBindBuffer(GL_ARRAY_BUFFER, 0);
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}
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void GLSnow::paint(OutputSurface& /*output*/)
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{
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	// Rotate and mirror noise texture in consecutive frames to avoid
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	// seeing 'patterns' in the noise.
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	static unsigned cnt = 0;
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	cnt = (cnt + 1) % 8;
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	vec2 offset(random_float(0.0f, 1.0f), random_float(0.0f, 1.0f));
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	const std::array tex = {
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		offset + vec2(0.0f, 2.0f),
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		offset + vec2(2.0f, 2.0f),
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		offset + vec2(2.0f, 0.0f),
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		offset + vec2(0.0f, 0.0f),
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	};
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	const auto& glContext = *gl::context;
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	glContext.progTex.activate();
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	glUniform4f(glContext.unifTexColor, 1.0f, 1.0f, 1.0f, 1.0f);
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	mat4 I;
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	glUniformMatrix4fv(glContext.unifTexMvp, 1, GL_FALSE, I.data());
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	glBindBuffer(GL_ARRAY_BUFFER, vbo[0].get());
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	const vec2* base = nullptr;
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	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, base + 4 * cnt);
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	glEnableVertexAttribArray(0);
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	glBindBuffer(GL_ARRAY_BUFFER, vbo[1].get());
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	glBufferData(GL_ARRAY_BUFFER, sizeof(tex), tex.data(), GL_STREAM_DRAW);
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	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, nullptr);
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	glEnableVertexAttribArray(1);
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	noiseTexture.bind();
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	glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
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	glDisableVertexAttribArray(1);
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	glDisableVertexAttribArray(0);
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	glBindBuffer(GL_ARRAY_BUFFER, 0);
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	display.repaintDelayed(100 * 1000); // 10fps
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}
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} // namespace openmsx