Minimal bgfx example to show D3D11 IB warning

cubes.cpp

/*
 * Copyright 2011-2019 Branimir Karadzic. All rights reserved.
 * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause
 */

#include "common.h"
#include "bgfx_utils.h"
#include "imgui/imgui.h"

namespace
{
// Copied from debugdraw.cpp
uint32_t genSphere(uint8_t _subdiv0, void* _pos0 = NULL, uint16_t _posStride0 = 0, void* _normals0 = NULL, uint16_t _normalStride0 = 0)
{
	if (NULL != _pos0) {
		struct Gen
		{
			Gen(void* _pos, uint16_t _posStride, void* _normals, uint16_t _normalStride, uint8_t _subdiv)
				: m_pos((uint8_t*)_pos)
				, m_normals((uint8_t*)_normals)
				, m_posStride(_posStride)
				, m_normalStride(_normalStride)
			{
				static const float scale = 1.0f;
				static const float golden = 1.6180339887f;
				static const float len = bx::sqrt(golden*golden + 1.0f);
				static const float ss = 1.0f / len * scale;
				static const float ll = ss * golden;

				static const bx::Vec3 vv[] =
				{
					{ -ll, 0.0f, -ss },
					{  ll, 0.0f, -ss },
					{  ll, 0.0f,  ss },
					{ -ll, 0.0f,  ss },

					{ -ss,  ll, 0.0f },
					{  ss,  ll, 0.0f },
					{  ss, -ll, 0.0f },
					{ -ss, -ll, 0.0f },

					{ 0.0f, -ss,  ll },
					{ 0.0f,  ss,  ll },
					{ 0.0f,  ss, -ll },
					{ 0.0f, -ss, -ll },
				};

				m_numVertices = 0;

				triangle(vv[0], vv[4], vv[3], scale, _subdiv);
				triangle(vv[0], vv[10], vv[4], scale, _subdiv);
				triangle(vv[4], vv[10], vv[5], scale, _subdiv);
				triangle(vv[5], vv[10], vv[1], scale, _subdiv);
				triangle(vv[5], vv[1], vv[2], scale, _subdiv);
				triangle(vv[5], vv[2], vv[9], scale, _subdiv);
				triangle(vv[5], vv[9], vv[4], scale, _subdiv);
				triangle(vv[3], vv[4], vv[9], scale, _subdiv);

				triangle(vv[0], vv[3], vv[7], scale, _subdiv);
				triangle(vv[0], vv[7], vv[11], scale, _subdiv);
				triangle(vv[11], vv[7], vv[6], scale, _subdiv);
				triangle(vv[11], vv[6], vv[1], scale, _subdiv);
				triangle(vv[1], vv[6], vv[2], scale, _subdiv);
				triangle(vv[2], vv[6], vv[8], scale, _subdiv);
				triangle(vv[8], vv[6], vv[7], scale, _subdiv);
				triangle(vv[8], vv[7], vv[3], scale, _subdiv);

				triangle(vv[0], vv[11], vv[10], scale, _subdiv);
				triangle(vv[1], vv[10], vv[11], scale, _subdiv);
				triangle(vv[2], vv[8], vv[9], scale, _subdiv);
				triangle(vv[3], vv[9], vv[8], scale, _subdiv);
			}

			void addVert(const bx::Vec3& _v)
			{
				bx::store(m_pos, _v);
				m_pos += m_posStride;

				if (NULL != m_normals) {
					const bx::Vec3 normal = bx::normalize(_v);
					bx::store(m_normals, normal);

					m_normals += m_normalStride;
				}

				m_numVertices++;
			}

			void triangle(const bx::Vec3& _v0, const bx::Vec3& _v1, const bx::Vec3& _v2, float _scale, uint8_t _subdiv)
			{
				if (0 == _subdiv) {
					addVert(_v0);
					addVert(_v1);
					addVert(_v2);
				} else {
					const bx::Vec3 v01 = bx::mul(bx::normalize(bx::add(_v0, _v1)), _scale);
					const bx::Vec3 v12 = bx::mul(bx::normalize(bx::add(_v1, _v2)), _scale);
					const bx::Vec3 v20 = bx::mul(bx::normalize(bx::add(_v2, _v0)), _scale);

					--_subdiv;
					triangle(_v0, v01, v20, _scale, _subdiv);
					triangle(_v1, v12, v01, _scale, _subdiv);
					triangle(_v2, v20, v12, _scale, _subdiv);
					triangle(v01, v12, v20, _scale, _subdiv);
				}
			}

			uint8_t* m_pos;
			uint8_t* m_normals;
			uint16_t m_posStride;
			uint16_t m_normalStride;
			uint32_t m_numVertices;

		} gen(_pos0, _posStride0, _normals0, _normalStride0, _subdiv0);
	}

	uint32_t numVertices = 20 * 3 * bx::uint32_max(1, (uint32_t)bx::pow(4.0f, _subdiv0));
	return numVertices;
}

struct PosColorVertex
{
	float m_x;
	float m_y;
	float m_z;
	uint32_t m_abgr;

	static void init()
	{
		ms_layout
			.begin()
			.add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float)
			.add(bgfx::Attrib::Color0,   4, bgfx::AttribType::Uint8, true)
			.end();
	};

	static bgfx::VertexLayout ms_layout;
};

bgfx::VertexLayout PosColorVertex::ms_layout;

static PosColorVertex s_cubeVertices[] =
{
	{-1.0f,  1.0f,  1.0f, 0xff000000 },
	{ 1.0f,  1.0f,  1.0f, 0xff0000ff },
	{-1.0f, -1.0f,  1.0f, 0xff00ff00 },
	{ 1.0f, -1.0f,  1.0f, 0xff00ffff },
	{-1.0f,  1.0f, -1.0f, 0xffff0000 },
	{ 1.0f,  1.0f, -1.0f, 0xffff00ff },
	{-1.0f, -1.0f, -1.0f, 0xffffff00 },
	{ 1.0f, -1.0f, -1.0f, 0xffffffff },
};

static const uint16_t s_cubeTriList[] =
{
	0, 1, 2, // 0
	1, 3, 2,
	4, 6, 5, // 2
	5, 6, 7,
	0, 2, 4, // 4
	4, 2, 6,
	1, 5, 3, // 6
	5, 7, 3,
	0, 4, 1, // 8
	4, 5, 1,
	2, 3, 6, // 10
	6, 3, 7,
};

static const uint32_t s_colors[] = {
	0xffff0000,
	0xff00ff00,
	0xff0000ff,
	0xffff00ff
};

class ExampleCubes : public entry::AppI
{
public:
	ExampleCubes(const char* _name, const char* _description, const char* _url)
		: entry::AppI(_name, _description, _url)
		, m_pt(0)
		, m_r(true)
		, m_g(true)
		, m_b(true)
		, m_a(true)
	{
	}

	void init(int32_t _argc, const char* const* _argv, uint32_t _width, uint32_t _height) override
	{
		Args args(_argc, _argv);

		m_width  = _width;
		m_height = _height;
		m_debug  = BGFX_DEBUG_NONE;
		m_reset  = BGFX_RESET_VSYNC;

		bgfx::Init init;
		init.type     = args.m_type;
		init.vendorId = args.m_pciId;
		init.resolution.width  = m_width;
		init.resolution.height = m_height;
		init.resolution.reset  = m_reset;
		bgfx::init(init);

		// Enable debug text.
		bgfx::setDebug(m_debug);

		// Set view 0 clear state.
		bgfx::setViewClear(0
			, BGFX_CLEAR_COLOR|BGFX_CLEAR_DEPTH
			, 0x303030ff
			, 1.0f
			, 0
			);

		// Create vertex stream declaration.
		PosColorVertex::init();

		// JD: Generate vertex and index buffer data. In my case, the data are generated
		// every frame.
		{
			bx::DefaultAllocator allocator;

			const uint8_t subdiv = 4;
			const uint32_t numSphereVertices = genSphere(subdiv);
			bx::Vec3* sphereVertices = (bx::Vec3*)BX_ALLOC(&allocator, sizeof(bx::Vec3) * numSphereVertices);
			genSphere(subdiv, sphereVertices, sizeof(bx::Vec3));

			const uint32_t numSphereIndices = numSphereVertices;

			// Fit as many spheres as we can in a single VB with 16-bit indices.
			const uint32_t numSpheres = 65536 / numSphereVertices;
			m_vbDataSize = sizeof(PosColorVertex) * numSphereVertices * numSpheres;
			m_vbData = (PosColorVertex*)BX_ALLOC(&allocator, m_vbDataSize);
			PosColorVertex* vbDataPtr = m_vbData;
			for (uint32_t i = 0; i < numSpheres; ++i) {
				const float posx = -15.0f + i * 8.0f;
				const float posy = 0.0f;
				const float posz = 0.0f;
				const uint32_t color = s_colors[i % BX_COUNTOF(s_colors)];

				for (uint32_t j = 0; j < numSphereVertices; j++) {
					vbDataPtr[j].m_x = posx + sphereVertices[j].x;
					vbDataPtr[j].m_y = posy + sphereVertices[j].y;
					vbDataPtr[j].m_z = posz + sphereVertices[j].z;
					vbDataPtr[j].m_abgr = color;
				}

				vbDataPtr += numSphereVertices;
			}

			// Generate a large enough IB to trigger the warning
			const uint32_t targetIBSize = 4 << 20; // This should be larger than BGFX_CONFIG_DYNAMIC_INDEX_BUFFER_SIZE
			m_instanceIndices = numSphereIndices * numSpheres;
			const uint32_t instanceIBMem = sizeof(uint16_t) * m_instanceIndices;
			m_numInstances = targetIBSize / instanceIBMem;

			m_ibDataSize = instanceIBMem * m_numInstances;
			m_ibData = (uint16_t*)BX_ALLOC(&allocator, m_ibDataSize);

			uint16_t* ibDataPtr = m_ibData;
			for (uint32_t i = 0; i < m_numInstances; ++i) {
				for (uint32_t j = 0; j < numSpheres; ++j) {
					const uint16_t baseVertex = (uint16_t)(j * numSphereVertices);

					for (uint32_t k = 0; k < numSphereIndices; ++k) {
						ibDataPtr[k] = (uint16_t)(baseVertex + k);
					}
					ibDataPtr += numSphereIndices;
				}
			}

			// Emulate a real-world scenario by preallocating both buffers to predefined values
			// even though, in this case, we know the exact numbers.
			// Note that setting the initial IB size to 256 will force all draw commands of the
			// initial couple of frames to be partially rendered (only 256 indices will be submitted)
			m_vbh = bgfx::createDynamicVertexBuffer(65536, PosColorVertex::ms_layout);
			m_ibh = bgfx::createDynamicIndexBuffer(256, BGFX_BUFFER_ALLOW_RESIZE);
		}

		// Create program from shaders.
		m_program = loadProgram("vs_cubes", "fs_cubes");

		m_timeOffset = bx::getHPCounter();

		imguiCreate();
	}

	virtual int shutdown() override
	{
		imguiDestroy();

		// Cleanup.
		bgfx::destroy(m_ibh);
		bgfx::destroy(m_vbh);
		bgfx::destroy(m_program);

		// Shutdown bgfx.
		bgfx::shutdown();

		return 0;
	}

	bool update() override
	{
		if (!entry::processEvents(m_width, m_height, m_debug, m_reset, &m_mouseState) )
		{
			imguiBeginFrame(m_mouseState.m_mx
				,  m_mouseState.m_my
				, (m_mouseState.m_buttons[entry::MouseButton::Left  ] ? IMGUI_MBUT_LEFT   : 0)
				| (m_mouseState.m_buttons[entry::MouseButton::Right ] ? IMGUI_MBUT_RIGHT  : 0)
				| (m_mouseState.m_buttons[entry::MouseButton::Middle] ? IMGUI_MBUT_MIDDLE : 0)
				,  m_mouseState.m_mz
				, uint16_t(m_width)
				, uint16_t(m_height)
				);

			showExampleDialog(this);

			imguiEndFrame();

			const bx::Vec3 at  = { 0.0f, 0.0f,   0.0f };
			const bx::Vec3 eye = { 0.0f, 0.0f, -35.0f };

			// Set view and projection matrix for view 0.
			{
				float view[16];
				bx::mtxLookAt(view, eye, at);

				float proj[16];
				bx::mtxProj(proj, 60.0f, float(m_width)/float(m_height), 0.1f, 100.0f, bgfx::getCaps()->homogeneousDepth);
				bgfx::setViewTransform(0, view, proj);

				// Set view 0 default viewport.
				bgfx::setViewRect(0, 0, 0, uint16_t(m_width), uint16_t(m_height) );
			}

			// This dummy draw call is here to make sure that view 0 is cleared
			// if no other draw calls are submitted to view 0.
			bgfx::touch(0);

			uint64_t state = 0
				| (m_r ? BGFX_STATE_WRITE_R : 0)
				| (m_g ? BGFX_STATE_WRITE_G : 0)
				| (m_b ? BGFX_STATE_WRITE_B : 0)
				| (m_a ? BGFX_STATE_WRITE_A : 0)
				| BGFX_STATE_WRITE_Z
				| BGFX_STATE_DEPTH_TEST_LESS
				| BGFX_STATE_CULL_CW
				| BGFX_STATE_MSAA
				;

			// JD: Submit all draw commands before updating the buffers.
			for (uint32_t i = 0; i < m_numInstances; ++i) {
				float mtx[16];
				bx::mtxIdentity(mtx);
				mtx[12] = -15.0f + (i % 2) * 32.0f;
				mtx[13] = -15.0f + (i / 2) * 2.0f;
				mtx[14] = 0.0f;

				bgfx::setTransform(mtx);
				bgfx::setVertexBuffer(0, m_vbh);
				bgfx::setIndexBuffer(m_ibh, m_instanceIndices * i, m_instanceIndices);
				bgfx::setState(state);
				bgfx::submit(0, m_program);
			}

			bgfx::update(m_vbh, 0, bgfx::makeRef(m_vbData, m_vbDataSize));
			bgfx::update(m_ibh, 0, bgfx::makeRef(m_ibData, m_ibDataSize));

			// Advance to next frame. Rendering thread will be kicked to
			// process submitted rendering primitives.
			bgfx::frame();

			return true;
		}

		return false;
	}

	entry::MouseState m_mouseState;

	uint32_t m_width;
	uint32_t m_height;
	uint32_t m_debug;
	uint32_t m_reset;
	bgfx::DynamicVertexBufferHandle m_vbh;
	bgfx::DynamicIndexBufferHandle m_ibh;
	bgfx::ProgramHandle m_program;
	int64_t m_timeOffset;
	int32_t m_pt;

	PosColorVertex* m_vbData;
	uint16_t* m_ibData;
	uint32_t m_vbDataSize;
	uint32_t m_ibDataSize;
	uint32_t m_numInstances;
	uint32_t m_instanceIndices;

	bool m_r;
	bool m_g;
	bool m_b;
	bool m_a;
};

} // namespace

ENTRY_IMPLEMENT_MAIN(
	  ExampleCubes
	, "01-cubes"
	, "Rendering simple static mesh."
	, "https://bkaradzic.github.io/bgfx/examples.html#cubes"
	);