Question

我似乎错误地使用了 glMultiDrawIndirect （MDI）和/或 DrawElementsIndirectCommand （DEIC），因为我无法正确渲染所有对象。尝试对相似的对象和纹理重复使用绘制命令的方法（“实例化” ... ish）会在所有位置绘制所有对象。 “调试”方法仅对每个对象（两个三角形）使用1个绘制命令，但输出始终是对象太少，第一个对象的位置永远不会用于任何对象。

使用实例化失败的尝试时，会发生以下情况：

在每个DEIC中使用一个对象（两个三角形）的“调试”方法时，会发生这种情况：

目标是正确使用DEIC中的instanceCount，以允许实例化，同时在正确的位置绘制正确数量的对象。我在Google突袭中的冒险经历表明，如果DEIC存储在缓冲区中，则DEIC 的baseInstance字段可以用作drawID。如果这是不可能的，或者如果我对用途有极大的误解，请打电话给我，让我知道！我已尝试使用尽可能少的适用代码，以避免发布10,000个字数的邮件。

下面，我正在创建“绘制路径”对象，这些对象是要加载到缓冲区中的缓冲区ID和向量的集合（基于与此问题无关的众多变量）。

// VAO glGenVertexArrays(1, &p->vertexArrayObject); glBindVertexArray(p->vertexArrayObject); // vertices glCreateBuffers(1, &p->vertexBuffer); glBindVertexBuffer(bindingIndex, p->vertexBuffer, 0, sizeof(Vertex)); glEnableVertexArrayAttrib(p->vertexArrayObject, 0); glEnableVertexArrayAttrib(p->vertexArrayObject, 1); glVertexAttribFormat(0, 3, GL_FLOAT, GL_FALSE, offsetof(Vertex, position)); glVertexAttribBinding(0, bindingIndex); glVertexAttribFormat(1, 2, GL_FLOAT, GL_TRUE, offsetof(Vertex, uv)); glVertexAttribBinding(1, bindingIndex); if(p->pathType == DrawPathType::FAST) { glNamedBufferStorage(p->vertexBuffer, p->rbVertices.bufferSize, nullptr, m_persistentCreateFlags); p->rbVertices.ptr = (Vertex*)glMapNamedBufferRange(p->vertexBuffer, 0, p->rbVertices.bufferSize, m_persistentMapFlags); p->rbVertices.bufferFragment = p->rbVertices.bufferSize / 3; } // indices glCreateBuffers(1, &p->indexBuffer); glVertexArrayElementBuffer(p->vertexArrayObject, p->indexBuffer); // draw commands // glCreateBuffers(1, &p->drawCmdBuffer); // glBindBuffer(GL_DRAW_INDIRECT_BUFFER, p->drawCmdBuffer); // glNamedBufferStorage(p->drawCmdBuffer, p->rbCommands.bufferSize, nullptr, m_persistentCreateFlags); // p->rbCommands.ptr = (DEIC*)glMapNamedBufferRange(p->drawCmdBuffer, 0, p->rbCommands.bufferSize, m_persistentMapFlags); // p->rbCommands.bufferFragment = p->rbCommands.bufferSize / 3; // unsure how this works // glEnableVertexArrayAttrib(p->vertexArrayObject, 2); // glVertexAttribIFormat(2, 1, GL_UNSIGNED_INT, offsetof(DrawElementsIndirectCommand, baseInstance)); // glVertexAttribBinding(2, bindingIndex); // glVertexBindingDivisor(bindingIndex, 1); // draw IDs glCreateBuffers(1, &p->drawIDBuffer); glBindBuffer(GL_ARRAY_BUFFER, p->drawIDBuffer); glEnableVertexAttribArray(2); glVertexAttribIPointer(2, 1, GL_UNSIGNED_INT, sizeof(GLuint), 0); glVertexAttribDivisor(2, 1); // transforms glCreateBuffers(1, &p->transformBuffer); if(p->pathType == DrawPathType::LONG || p->pathType == DrawPathType::FAST) { glNamedBufferStorage(p->transformBuffer, p->rbTransforms.bufferSize, nullptr, m_persistentCreateFlags); p->rbTransforms.ptr = (glm::mat4*)glMapNamedBufferRange(p->transformBuffer, 0, p->rbTransforms.bufferSize, m_persistentMapFlags); p->rbTransforms.bufferFragment = p->rbTransforms.bufferSize / 3; glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, p->transformBuffer); } // texture addresses glCreateBuffers(1, &p->textureAddressBuffer); glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, p->textureAddressBuffer);

这是“ renderPrep”功能的有用部分。

for(size_t i = 0; i < glyphs->size(); i++) { auto it = glyphs->at(i); // ensure we have a valid texture address if(!it->textureAddress.defined()) { Logger::getInstance().Log(Logs::CRIT, Logs::Drawing, "Renderer2D::drawPrep()", "Iteration [{}] of [{}] has a null texture address (0,0)!", i, glyphs->size()); failed++; } else { offset = verts->size(); for(int in = 0; in < QUAD_VERTS; in++) { indices->push_back(baseQuadIndices[in] + offset); } // creating our model space to world space matrix ('model' in "projection * view * model") glm::mat4 transRotate = glm::rotate(identMat, glm::radians(it->angle), glm::vec3(0.0f, 0.0f, 1.0f)); transforms->push_back(transRotate); transforms->back() = glm::translate(transforms->back(), it->position); // push back modelspace vertices for(auto& v : it->vertices) { verts->push_back(v); } // update previous draw command or create a new one if(currentTex.exists() && currentTex == it->textureAddress) { // append previous draw command DEICs->back().vertexCount += QUAD_VERTS; DEICs->back().instanceCount += 1; // two triangles, thus two instances } else { // different texture, new draw command DEIC tmp = { QUAD_VERTS, 1, (inc * QUAD_VERTS), (inc * BASE_VERTS), inc }; DEICs->push_back(tmp); currentTex = it->textureAddress; } /// \NOTE: Current issue is that the draw command is only drawing one object, in two iterations. /// This is responsible for the blank second box /* DEIC tmp = { QUAD_VERTS, 1, (inc * QUAD_VERTS), (inc * BASE_VERTS), 0 }; DEICs->push_back(tmp); texAddrs->push_back(it->textureAddress); */ Logger::getInstance().Log(Logs::DEBUG, Logs::Drawing, "Renderer2D::drawPrep()", "\n\033[93mDEIC #{}\033[0m:\n\tvertCount\t\t{}\n\tinstCount\t\t{}\n\tfirstInd\t\t{}\n\tbaseVert\t\t{}\n\tbaseInst\t\t{}\n", DEICs->size(), DEICs->back().vertexCount, DEICs->back().instanceCount, DEICs->back().firstIndex, DEICs->back().baseVertex, DEICs->back().baseInstance); texAddrs->push_back(currentTex); p->drawIDs.push_back(inc); inc++; } }

这是实际上负责渲染的代码段。

int activeProgramID = 0; // currently used glsl program glGetIntegerv(GL_CURRENT_PROGRAM, &activeProgramID); // active passed glsl program id, or enable existing if not already enabled if(glProgID > 0) { glUseProgram(glProgID); } else if(activeProgramID == 0) { glUseProgram(m_prog->getProgramID()); } // all clear, do it! glBindVertexArray(p->vertexArrayObject); // bind SSBOs, if applicable if(p->transformBuffer) { glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, p->transformBuffer); } if(p->textureAddressBuffer) { glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, p->textureAddressBuffer); } // finally render //if(p->drawCmdBuffer) { glBindBuffer(GL_DRAW_INDIRECT_BUFFER, p->drawCmdBuffer); glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, 0, p->drawCommands.size(), 0); } //else { glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, p->drawCommands.data(), p->drawCommands.size(), 0); } glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, p->drawCommands.data(), p->drawCommands.size(), 0); // update ring buffer(s), if applicable if(p->rbCommands.ptr != nullptr) { m_bufferLockManager->lockRange(p->rbCommands.oldHead, p->rbCommands.bufferFragment); } if(p->rbTransforms.ptr != nullptr) { m_bufferLockManager->lockRange(p->rbTransforms.oldHead, p->rbTransforms.bufferFragment); } if(p->rbVertices.ptr != nullptr) { m_bufferLockManager->lockRange(p->rbVertices.oldHead, p->rbVertices.bufferFragment); } // options specific to a "fast" draw path (if a fast draw path, glyphs are single use) if(p->pathType == DrawPathType::FAST) { p->clear(true); } // clean up glBindVertexArray(0); // change to previous glProgram if(activeProgramID) { glUseProgram(activeProgramID); } else { glUseProgram(0); }

编辑＃1，2019-04-05 11：53a EST ：

首先，我忘记了着色器！很抱歉错过这个机会。

// --------- Vertex shader ------------ // uniforms / shader_storage_buffer object layout(std140, binding = 0) buffer CB0 { mat4 Transforms[]; }; // view & projection in one uniform mat4 ViewProjection; // input layout(location = 0) in vec3 In_v3Pos; layout(location = 1) in vec2 In_v2TexCoord; layout(location = 2) in uint In_uiDrawID; // output out DrawBlock { vec2 v2TexCoord; flat uint iDrawID; } Out; void main() { mat4 World = Transforms[In_uiDrawID + gl_InstanceID]; vec4 worldPos = World * vec4(In_v3Pos, 1.0); gl_Position = ViewProjection * worldPos; Out.v2TexCoord = In_v2TexCoord; Out.iDrawID = In_uiDrawID; } // --------- Fragment shader ------------ struct TexAddress { sampler2DArray arr; float slice; }; layout (std430, binding = 1) buffer CB1 { TexAddress texAddress[]; }; // input in DrawBlock { vec2 v2TexCoord; flat uint iDrawID; } In; // output layout(location = 0) out vec4 Out_v4Color; vec4 Texture(TexAddress addr, vec2 uv) { return texture(addr.arr, vec3(uv, addr.slice)); } void main() { int DrawID = int(In.iDrawID); Out_v4Color = vec4(Texture(texAddress[DrawID], In.v2TexCoord).xyz, 1.0f); }

如果我使用非DSA删除了drawIDs块并替换为以下代码段，则会绘制白色三角形，重点放在屏幕中心。

glCreateBuffers(1, &p->drawCmdBuffer); glBindBuffer(GL_DRAW_INDIRECT_BUFFER, p->drawCmdBuffer); glNamedBufferStorage(p->drawCmdBuffer, p->rbCommands.bufferSize, nullptr, m_persistentCreateFlags); p->rbCommands.ptr = (DEIC*)glMapNamedBufferRange(p->drawCmdBuffer, 0, p->rbCommands.bufferSize, m_persistentMapFlags); p->rbCommands.bufferFragment = p->rbCommands.bufferSize / 3; glEnableVertexArrayAttrib(p->vertexArrayObject, 2); glVertexAttribIFormat(2, 1, GL_UNSIGNED_INT, offsetof(DrawElementsIndirectCommand, baseInstance)); glVertexAttribBinding(2, bindingIndex); glVertexBindingDivisor(2, 1);

结果：

编辑＃2 @ 2019-04-06 12：09p EST ：在github上创建了一个gist，其中包含渲染器的完整标题/源。链接：https://gist.github.com/bbilyeu/bbf74ef4eaf979b5d2b4f2c2a9dcce48

Answer 1

元素，实例和绘制命令的数量都不同，并且引用的事物也不同。特别是，使用任何多绘制命令并不一定意味着您要进行任何实例化。

以下代码使用一个glMultiDrawArraysIndirect调用发出两个绘图命令：

呈现三个“ quad”对象的实例
渲染“三角形”对象的五个实例

数据

struct Vert {
    vec2f position;
};

struct Inst {
    box2f position;
    vec4f color;
};

static const Vert verts[] = {
    // quad
    { { 0, 0 } },
    { { 1, 0 } },
    { { 0, 1 } },
    { { 1, 1 } },

    // triangle
    { { 0, 0 } },
    { { 1, 0 } },
    { { 0.5, 1 } },
};

static const Inst insts[] = {
    // three quads
    { { -0.8, -0.8, -0.6, -0.6 }, { 1, 0, 0, 1 } },
    { { -0.1, -0.8, 0.1, -0.6 }, { 0, 1, 0, 1 } },
    { { 0.6, -0.8, 0.8, -0.6 }, { 0, 0, 1, 1 } },

    // five triangles
    { { -0.8, 0.6, -0.6, 0.8 }, { 1, 1, 0, 1 } },
    { { -0.4, 0.6, -0.2, 0.8 }, { 0.1, 0.1, 0.1, 1 } },
    { { -0.1, 0.6, 0.1, 0.8 }, { 0, 1, 1, 1 } },
    { { 0.2, 0.6, 0.4, 0.8 }, { 0.1, 0.1, 0.1, 1 } },
    { { 0.6, 0.6, 0.8, 0.8 }, { 1, 0, 1, 1 } },
};

static const DrawArraysIndirectCommandSN cmds[] = {
    // quads: 4 vertices, 3 instances, first vertex=0, first instance=0
    { 4, 3, 0, 0 },

    // triangles: 3 vertices, 5 instances, first vertex=4, first instance=3
    { 3, 5, 4, 3 },
};

初始化代码：

GLuint buf[3]; // vertex, instance, draw-command buffers
glCreateBuffers(3, buf);
glNamedBufferStorage(buf[0], sizeof(verts), verts, 0);
glNamedBufferStorage(buf[1], sizeof(insts), insts, 0);
glNamedBufferStorage(buf[2], sizeof(cmds), cmds, 0);

GLuint va;
glCreateVertexArrays(1, &va);
glVertexArrayVertexBuffer(va, 0, buf[0], 0, sizeof(Vert));
glVertexArrayVertexBuffer(va, 1, buf[1], 0, sizeof(Inst));
glVertexArrayBindingDivisor(va, 1, 1);
glVertexArrayAttribBinding(va, 0, 0);
glEnableVertexArrayAttrib(va, 0);
glVertexArrayAttribFormat(va, 0, 2, GL_FLOAT, 0, offsetof(Vert, position));
glVertexArrayAttribBinding(va, 1, 1);
glEnableVertexArrayAttrib(va, 1);
glVertexArrayAttribFormat(va, 1, 4, GL_FLOAT, 0, offsetof(Inst, position));
glVertexArrayAttribBinding(va, 2, 1);
glEnableVertexArrayAttrib(va, 2);
glVertexArrayAttribFormat(va, 2, 4, GL_FLOAT, 0, offsetof(Inst, color));

渲染部分：

glClear(GL_COLOR_BUFFER_BIT);
glBindProgramPipeline(pp.get());
glBindVertexArray(va);
glBindBuffer(GL_DRAW_INDIRECT_BUFFER, buf[2]);
glMultiDrawArraysIndirect(GL_TRIANGLE_STRIP, 0, sizeof(cmds)/sizeof(cmds[0]), 0);

顶点着色器：

#version 450 core
layout(location = 0) in vec2 position;
layout(location = 1) in vec4 inst_position;
layout(location = 2) in vec4 color;

out gl_PerVertex {
    vec4 gl_Position;
};

layout(location = 0) out PerVertex {
    vec4 color;
} OUT;

void main() {
    OUT.color = color;
    gl_Position = vec4(mix(inst_position.xy, inst_position.zw, position), 0, 1);
}

片段着色器：

#version 450 core
layout(location = 0) in PerVertex {
    vec4 color;
} IN;
layout(location = 0) out vec4 OUT;
void main() {
    OUT = IN.color;
}

glMultiDrawIndirect和DrawElementsIndirectCommands无法呈现所有对象

1 个答案:

数据

初始化代码：

渲染部分：

顶点着色器：

片段着色器：

结果：