geometry.cpp

#include "geometry.hpp"
//#include "math.hpp"
namespace math {
	inline uint32_t float4_to_rgba8(const float *in_color) {
		uint32_t color = 0;
		color |= uint32_t(uint8_t(in_color[0] * 255) << 0);
		color |= uint32_t(uint8_t(in_color[1] * 255) << 8);
		color |= uint32_t(uint8_t(in_color[2] * 255) << 16);
		color |= uint32_t(uint8_t(in_color[3] * 255) << 24);
		return color;
	}
}
#include <bx/fpumath.h>
#include <bgfx/bgfx.h>
#include <vector>
#include <cstdint>

using namespace myon;

namespace {
	const float red[4]   = { 1.0f, 0.0f, 0.0f, 1.0f };
	const float green[4] = { 0.0f, 1.0f, 0.0f, 1.0f };
	const float blue[4]  = { 0.0f, 0.0f, 1.0f, 1.0f };

	// fallback color
	const uint32_t white = 0xffffffff;

	const int cube_indices[] = {
		// sides
		0, 4,
		1, 5,
		2, 6,
		3, 7,

		// top
		0, 1,
		0, 3,
		2, 3,
		2, 1,

		// bottom
		4, 5,
		4, 7,
		6, 7,
		6, 5
	};

	const float mtx_identity[] = {
		1.0f, 0.0f, 0.0f, 0.0f,
		0.0f, 1.0f, 0.0f, 0.0f,
		0.0f, 0.0f, 1.0f, 0.0f,
		0.0f, 0.0f, 0.0f, 1.0f
	};

	struct vertex_t {
		float position[3];
		uint32_t color;
	};
	std::vector<vertex_t> buffer;
}

void graphics::draw_line(const float *start, const float *end, const float *color, const float *mtx) {
	const float *_mtx = mtx ? mtx : mtx_identity; 
	vertex_t v1, v2;
	bx::vec3MulMtx(v1.position, start, _mtx);
	bx::vec3MulMtx(v2.position, end, _mtx);
	v1.color = v2.color = color ? math::float4_to_rgba8(color) : white;
	buffer.push_back(v1);
	buffer.push_back(v2);
}

void graphics::draw_grid(const float *position, int num_lines, float spacing, const float *color, const float *mtx) {
	float v1[3], v2[3];
	bx::vec3Move(v1, position);
	bx::vec3Move(v2, position);

	// X
	float line_length = spacing * (num_lines/2);
	v1[1] = position[1] - line_length;
	v2[1] = position[1] + line_length;
	for (int i = -num_lines/2; i <= num_lines/2; i++) {
		v1[0] = position[0] + spacing * i;
		v2[0] = v1[0];
		draw_line(v1, v2, color, mtx);
	}

	// Y
	v1[0] = position[0] - line_length;
	v2[0] = position[0] + line_length;
	for (int i = -num_lines/2; i <= num_lines/2; i++) {
		v1[1] = position[1] + spacing * i;
		v2[1] = v1[1];
		draw_line(v1, v2, color, mtx);
	}
}

void graphics::draw_cube(const float *min, const float *max, const float *color, const float *mtx) {
	float vertices[] = {
		min[0], min[1], max[2],
		max[0], min[1], max[2],
		max[0], max[1], max[2],
		min[0], max[1], max[2],

		min[0], min[1], min[2],
		max[0], min[1], min[2],
		max[0], max[1], min[2],
		min[0], max[1], min[2]
	};
	vertex_t v1, v2;
	v1.color = v2.color = color ? math::float4_to_rgba8(color) : white;
	for (unsigned i = 1; i < BX_COUNTOF(cube_indices); i+=2) {
		const float *_mtx = mtx ? mtx : mtx_identity;
		bx::vec3MulMtx(v1.position, &vertices[cube_indices[i-1]*3], _mtx);
		bx::vec3MulMtx(v2.position, &vertices[cube_indices[i]  *3], _mtx);
		buffer.push_back(v1);
		buffer.push_back(v2);
	}
}

void graphics::draw_axis(const float *position, const float scale, const float *mtx) {
	float tmp[3];

	bx::vec3Move(tmp, position);
	tmp[0] += 1.0f * scale,
	draw_line(position, tmp, red, mtx);

	bx::vec3Move(tmp, position);
	tmp[1] += 1.0f * scale,
	draw_line(position, tmp, green, mtx);

	bx::vec3Move(tmp, position);
	tmp[2] += 1.0f * scale,
	draw_line(position, tmp, blue, mtx);
}

void graphics::dump_geometry(bool clear_only) {
	if (clear_only) {
		buffer.clear();
		return;
	}

	static bool vertex_ready = false;
	static bgfx::VertexDecl decl;
	if (!vertex_ready) {
		decl.begin();
		decl.add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float);
		decl.add(bgfx::Attrib::Color0, 4, bgfx::AttribType::Uint8, true);
		decl.end();
	}
	if (bgfx::checkAvailTransientVertexBuffer(buffer.size(), decl)) {
		bgfx::TransientVertexBuffer vb;
		bgfx::allocTransientVertexBuffer(&vb, buffer.size(), decl);
		memcpy(vb.data, buffer.data(), buffer.size()*sizeof(vertex_t));
		bgfx::setVertexBuffer(&vb);
	}
	buffer.clear();
}

geometry.hpp

namespace myon {
namespace graphics {
void draw_line(const float *start, const float *end, const float *color = nullptr, const float *mtx = nullptr);
void draw_grid(const float *position, int num_lines = 16, float spacing = 1.0f, const float *color = nullptr, const float *mtx = nullptr);
void draw_cube(const float *min, const float *max, const float *color = nullptr, const float *mtx = nullptr);
void draw_axis(const float *position, const float scale = 1.0f, const float *mtx = nullptr);
void dump_geometry(bool clear_only = false);
} // graphics
} // myon