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Revert "ifcviewer: MDI compaction via glMultiDrawElementsIndirectCount"

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This reverts commit d5b7b87ba17c90008cf0673c838ce8431ad85e36.
This commit is contained in:
Dion Moult
2026-04-17 18:34:01 +10:00
parent 4bedb40d8a
commit fc89ffeb19
3 changed files with 40 additions and 202 deletions
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src/ifcviewer/README.md
+4 -7
View File
@@ -809,12 +809,9 @@ single giant model / <18 cores CPU BVH trv Phase 3E GPU cull (plann
Occlusion halves survivors on dense interiors. Depth
pre-pass has same CP overhead as color pass (690k empty
sub-draws); cost dominated by MDI command processing.
- [x] MDI compaction — pack compute shader compacts non-empty
commands into contiguous fwd/rev ranges; drawn via
`glMultiDrawElementsIndirectCount` (GL 4.6 /
`ARB_indirect_parameters`, loaded via `getProcAddress`).
Eliminates ~690k empty sub-draws from both depth pre-pass
and color pass. Falls back to uncompacted MDI when the
entrypoint is unavailable.
- [ ] MDI compaction — compact non-empty commands into contiguous
buffer, use `glMultiDrawElementsIndirectCount` (GL 4.6 /
`ARB_indirect_parameters`). Deferred until all feature buckets
land so we can introduce GL 4.6 loading once, cleanly.
- [ ] Vulkan/MoltenVK backend for macOS
- [ ] Embedded Python scripting console
src/ifcviewer/ViewportWindow.cpp
+36 -186
View File
@@ -436,42 +436,6 @@ void main() {
}
)";
// Pack non-empty indirect commands from the source (4M) into a compact
// buffer. Forward commands [0..2M) pack to dst[0..], reverse [2M..4M) pack
// to dst[2M..]. Two atomic counters in counts[]: [0]=fwd, [1]=rev.
static const char* CULL_PACK_COMPUTE_SHADER = R"(
#version 450 core
layout(local_size_x = 64) in;
layout(std430, binding = 0) readonly buffer SrcBuf { uint src[]; };
layout(std430, binding = 1) writeonly buffer DstBuf { uint dst[]; };
layout(std430, binding = 2) coherent buffer CountBuf { uint counts[]; };
uniform uint u_total_cmds;
uniform uint u_fwd_cmds;
void main() {
uint i = gl_GlobalInvocationID.x;
if (i >= u_total_cmds) return;
uint ic = src[i * 5u + 1u];
if (ic == 0u) return;
bool is_fwd = (i < u_fwd_cmds);
uint slot = is_fwd ? atomicAdd(counts[0], 1u)
: atomicAdd(counts[1], 1u) + u_fwd_cmds;
dst[slot * 5u + 0u] = src[i * 5u + 0u];
dst[slot * 5u + 1u] = ic;
dst[slot * 5u + 2u] = src[i * 5u + 2u];
dst[slot * 5u + 3u] = src[i * 5u + 3u];
dst[slot * 5u + 4u] = src[i * 5u + 4u];
}
)";
#ifndef GL_PARAMETER_BUFFER_ARB
#define GL_PARAMETER_BUFFER_ARB 0x80EE
#endif
using PFN_glMultiDrawElementsIndirectCount = void (*)(
GLenum mode, GLenum type, const void* indirect,
GLintptr drawcount, GLsizei maxdrawcount, GLsizei stride);
static PFN_glMultiDrawElementsIndirectCount glMultiDrawElementsIndirectCount_ = nullptr;
static GLuint linkComputeProgram(QOpenGLFunctions_4_5_Core* gl, const char* src) {
GLuint cs = compileShader(gl, GL_COMPUTE_SHADER, src);
GLuint prog = gl->glCreateProgram();
@@ -654,8 +618,6 @@ ViewportWindow::~ViewportWindow() {
if (m.gpu_visible_ssbo) gl_->glDeleteBuffers(1, &m.gpu_visible_ssbo);
if (m.gpu_mesh_base_ssbo) gl_->glDeleteBuffers(1, &m.gpu_mesh_base_ssbo);
if (m.gpu_mesh_flags_ssbo) gl_->glDeleteBuffers(1, &m.gpu_mesh_flags_ssbo);
if (m.gpu_compacted_buffer) gl_->glDeleteBuffers(1, &m.gpu_compacted_buffer);
if (m.gpu_draw_count_buffer) gl_->glDeleteBuffers(1, &m.gpu_draw_count_buffer);
}
if (axis_vao_) gl_->glDeleteVertexArrays(1, &axis_vao_);
if (axis_vbo_) gl_->glDeleteBuffers(1, &axis_vbo_);
@@ -664,7 +626,6 @@ ViewportWindow::~ViewportWindow() {
if (axis_program_) gl_->glDeleteProgram(axis_program_);
if (cull_reset_program_) gl_->glDeleteProgram(cull_reset_program_);
if (cull_compact_program_) gl_->glDeleteProgram(cull_compact_program_);
if (cull_pack_program_) gl_->glDeleteProgram(cull_pack_program_);
if (hiz_gpu_depth_prog_) gl_->glDeleteProgram(hiz_gpu_depth_prog_);
if (hiz_gpu_copy_prog_) gl_->glDeleteProgram(hiz_gpu_copy_prog_);
if (hiz_gpu_reduce_prog_) gl_->glDeleteProgram(hiz_gpu_reduce_prog_);
@@ -769,20 +730,6 @@ void ViewportWindow::buildShaders() {
}
hiz_gpu_copy_prog_ = linkComputeProgram(gl_, HIZ_COPY_COMPUTE_SHADER);
hiz_gpu_reduce_prog_ = linkComputeProgram(gl_, HIZ_REDUCE_COMPUTE_SHADER);
cull_pack_program_ = linkComputeProgram(gl_, CULL_PACK_COMPUTE_SHADER);
if (!glMultiDrawElementsIndirectCount_) {
glMultiDrawElementsIndirectCount_ =
reinterpret_cast<PFN_glMultiDrawElementsIndirectCount>(
context_->getProcAddress("glMultiDrawElementsIndirectCount"));
if (!glMultiDrawElementsIndirectCount_) {
glMultiDrawElementsIndirectCount_ =
reinterpret_cast<PFN_glMultiDrawElementsIndirectCount>(
context_->getProcAddress("glMultiDrawElementsIndirectCountARB"));
}
if (!glMultiDrawElementsIndirectCount_)
qWarning("glMultiDrawElementsIndirectCount not available — MDI compaction disabled");
}
}
void ViewportWindow::buildAxisGizmo() {
@@ -1217,26 +1164,6 @@ void ViewportWindow::uploadGpuCullStaticBuffers(ModelGpuData& m) {
gl_->glNamedBufferSubData(m.gpu_mesh_flags_ssbo, 0,
M * sizeof(uint32_t), mesh_flags.data());
}
// Compacted indirect buffer — same capacity as the source buffer.
if (m.gpu_compacted_buffer && m.gpu_compacted_capacity < ind_bytes) {
gl_->glDeleteBuffers(1, &m.gpu_compacted_buffer);
m.gpu_compacted_buffer = 0;
m.gpu_compacted_capacity = 0;
}
if (!m.gpu_compacted_buffer) {
gl_->glCreateBuffers(1, &m.gpu_compacted_buffer);
gl_->glNamedBufferStorage(m.gpu_compacted_buffer, ind_bytes, nullptr,
GL_DYNAMIC_STORAGE_BIT);
m.gpu_compacted_capacity = ind_bytes;
}
// Draw-count buffer — 2 × uint32: [fwd_count, rev_count].
if (!m.gpu_draw_count_buffer) {
gl_->glCreateBuffers(1, &m.gpu_draw_count_buffer);
gl_->glNamedBufferStorage(m.gpu_draw_count_buffer, 2 * sizeof(uint32_t),
nullptr, GL_DYNAMIC_STORAGE_BIT);
}
}
void ViewportWindow::finalizeModel(uint32_t model_id) {
@@ -1317,8 +1244,6 @@ void ViewportWindow::applyCachedModel(uint32_t model_id, SidecarData data) {
if (existing->second.gpu_visible_ssbo) gl_->glDeleteBuffers(1, &existing->second.gpu_visible_ssbo);
if (existing->second.gpu_mesh_base_ssbo) gl_->glDeleteBuffers(1, &existing->second.gpu_mesh_base_ssbo);
if (existing->second.gpu_mesh_flags_ssbo) gl_->glDeleteBuffers(1, &existing->second.gpu_mesh_flags_ssbo);
if (existing->second.gpu_compacted_buffer) gl_->glDeleteBuffers(1, &existing->second.gpu_compacted_buffer);
if (existing->second.gpu_draw_count_buffer) gl_->glDeleteBuffers(1, &existing->second.gpu_draw_count_buffer);
models_gpu_.erase(existing);
}
@@ -1468,8 +1393,6 @@ void ViewportWindow::resetScene() {
if (m.gpu_visible_ssbo) gl_->glDeleteBuffers(1, &m.gpu_visible_ssbo);
if (m.gpu_mesh_base_ssbo) gl_->glDeleteBuffers(1, &m.gpu_mesh_base_ssbo);
if (m.gpu_mesh_flags_ssbo) gl_->glDeleteBuffers(1, &m.gpu_mesh_flags_ssbo);
if (m.gpu_compacted_buffer) gl_->glDeleteBuffers(1, &m.gpu_compacted_buffer);
if (m.gpu_draw_count_buffer) gl_->glDeleteBuffers(1, &m.gpu_draw_count_buffer);
}
models_gpu_.clear();
selected_object_id_ = 0;
@@ -1512,8 +1435,6 @@ void ViewportWindow::removeModel(uint32_t model_id) {
if (it->second.gpu_visible_ssbo) gl_->glDeleteBuffers(1, &it->second.gpu_visible_ssbo);
if (it->second.gpu_mesh_base_ssbo) gl_->glDeleteBuffers(1, &it->second.gpu_mesh_base_ssbo);
if (it->second.gpu_mesh_flags_ssbo) gl_->glDeleteBuffers(1, &it->second.gpu_mesh_flags_ssbo);
if (it->second.gpu_compacted_buffer) gl_->glDeleteBuffers(1, &it->second.gpu_compacted_buffer);
if (it->second.gpu_draw_count_buffer) gl_->glDeleteBuffers(1, &it->second.gpu_draw_count_buffer);
models_gpu_.erase(it);
have_cached_cull_ = false;
requestUpdate();
@@ -2314,35 +2235,8 @@ void ViewportWindow::render() {
gl_->glMemoryBarrier(GL_COMMAND_BARRIER_BIT | GL_SHADER_STORAGE_BARRIER_BIT);
};
const bool mdi_count_available =
glMultiDrawElementsIndirectCount_ && cull_pack_program_;
// Pack non-empty commands into contiguous fwd / rev ranges.
auto dispatchPack = [&]() {
if (!mdi_count_available) return;
for (auto& tgt : targets) {
ModelGpuData& m = *tgt.m;
const uint32_t total_cmds = m.gpu_mesh_command_count;
const uint32_t fwd_cmds = 2u * m.gpu_forward_command_count;
const uint32_t zero[2] = {0, 0};
gl_->glNamedBufferSubData(m.gpu_draw_count_buffer, 0,
sizeof(zero), zero);
gl_->glUseProgram(cull_pack_program_);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, m.gpu_indirect_buffer);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, m.gpu_compacted_buffer);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, m.gpu_draw_count_buffer);
gl_->glUniform1ui(gl_->glGetUniformLocation(cull_pack_program_, "u_total_cmds"),
total_cmds);
gl_->glUniform1ui(gl_->glGetUniformLocation(cull_pack_program_, "u_fwd_cmds"),
fwd_cmds);
gl_->glDispatchCompute((total_cmds + 63u) / 64u, 1, 1);
}
gl_->glMemoryBarrier(GL_COMMAND_BARRIER_BIT | GL_SHADER_STORAGE_BARRIER_BIT);
};
// Phase 1: cull without HiZ.
dispatchCull(false);
dispatchPack();
// Depth pre-pass: render phase 1 survivors into hiz_gpu_fbo_.
gl_->glBindFramebuffer(GL_FRAMEBUFFER, hiz_gpu_fbo_);
@@ -2358,31 +2252,17 @@ void ViewportWindow::render() {
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, m.ssbo);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, m.gpu_visible_ssbo);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, m.mesh_info_ssbo);
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_indirect_buffer);
const uint32_t M = m.gpu_forward_command_count;
if (mdi_count_available && m.gpu_compacted_buffer && m.gpu_draw_count_buffer) {
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_compacted_buffer);
gl_->glBindBuffer(GL_PARAMETER_BUFFER_ARB, m.gpu_draw_count_buffer);
gl_->glFrontFace(GL_CCW);
glMultiDrawElementsIndirectCount_(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
0, static_cast<GLsizei>(2u * M), 0);
gl_->glFrontFace(GL_CW);
glMultiDrawElementsIndirectCount_(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
sizeof(uint32_t), static_cast<GLsizei>(2u * M), 0);
} else {
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_indirect_buffer);
gl_->glFrontFace(GL_CCW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
static_cast<GLsizei>(2u * M), 0);
gl_->glFrontFace(GL_CW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
static_cast<GLsizei>(2u * M), 0);
}
gl_->glFrontFace(GL_CCW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
static_cast<GLsizei>(2u * M), 0);
gl_->glFrontFace(GL_CW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
static_cast<GLsizei>(2u * M), 0);
}
gl_->glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
@@ -2424,7 +2304,6 @@ void ViewportWindow::render() {
// the tighter set.
gl_->glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT);
dispatchCull(true);
dispatchPack();
gpu_cull_last_input_ = total_in;
gpu_cull_ns_ += t.nsecsElapsed();
@@ -2451,6 +2330,9 @@ void ViewportWindow::render() {
if (m.hidden || !m.ssbo || m.ssbo_instance_count == 0) continue;
if (gpu_cull_enabled) {
// GPU path: compact shader routed survivors into 4 buckets
// (fwd_lod0, fwd_lod1, rev_lod0, rev_lod1), each with M
// commands. CCW MDI for [0..2M), CW MDI for [2M..4M).
if (!m.gpu_indirect_buffer || !m.gpu_visible_ssbo ||
m.gpu_mesh_command_count == 0) continue;
@@ -2458,51 +2340,31 @@ void ViewportWindow::render() {
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, m.ssbo);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, m.gpu_visible_ssbo);
gl_->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, m.mesh_info_ssbo);
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_indirect_buffer);
const uint32_t M = m.gpu_forward_command_count;
if (glMultiDrawElementsIndirectCount_ &&
m.gpu_compacted_buffer && m.gpu_draw_count_buffer) {
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_compacted_buffer);
gl_->glBindBuffer(GL_PARAMETER_BUFFER_ARB, m.gpu_draw_count_buffer);
if (!skip_mdi) {
gl_->glFrontFace(GL_CCW);
glMultiDrawElementsIndirectCount_(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
0, static_cast<GLsizei>(2u * M), 0);
++gl_draw_calls_;
gl_->glFrontFace(GL_CW);
glMultiDrawElementsIndirectCount_(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
sizeof(uint32_t), static_cast<GLsizei>(2u * M), 0);
++gl_draw_calls_;
gl_->glFrontFace(GL_CCW);
}
} else {
gl_->glBindBuffer(GL_DRAW_INDIRECT_BUFFER, m.gpu_indirect_buffer);
uint32_t fwd = 2u * M;
uint32_t rev = 2u * M;
if (max_subdraws < m.gpu_mesh_command_count) {
const uint32_t total = m.gpu_mesh_command_count;
fwd = static_cast<uint32_t>((uint64_t)fwd * max_subdraws / total);
rev = max_subdraws - fwd;
}
if (fwd > 0 && !skip_mdi) {
gl_->glFrontFace(GL_CCW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
static_cast<GLsizei>(fwd), 0);
++gl_draw_calls_;
}
if (rev > 0 && !skip_mdi) {
gl_->glFrontFace(GL_CW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
static_cast<GLsizei>(rev), 0);
++gl_draw_calls_;
gl_->glFrontFace(GL_CCW);
}
uint32_t fwd = 2u * M; // fwd_lod0 + fwd_lod1
uint32_t rev = 2u * M; // rev_lod0 + rev_lod1
if (max_subdraws < m.gpu_mesh_command_count) {
const uint32_t total = m.gpu_mesh_command_count;
fwd = static_cast<uint32_t>((uint64_t)fwd * max_subdraws / total);
rev = max_subdraws - fwd;
}
if (fwd > 0 && !skip_mdi) {
gl_->glFrontFace(GL_CCW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT, nullptr,
static_cast<GLsizei>(fwd), 0);
++gl_draw_calls_;
}
if (rev > 0 && !skip_mdi) {
gl_->glFrontFace(GL_CW);
gl_->glMultiDrawElementsIndirect(
GL_TRIANGLES, GL_UNSIGNED_INT,
reinterpret_cast<const void*>(2u * M * sizeof(DrawElementsIndirectCommand)),
static_cast<GLsizei>(rev), 0);
++gl_draw_calls_;
gl_->glFrontFace(GL_CCW);
}
indirect_sub_draws_ += m.gpu_mesh_command_count;
continue;
@@ -2635,18 +2497,6 @@ void ViewportWindow::render() {
gpu_cull_last_survivors_ = gpu_surv;
visible_objects_ = gpu_obj;
visible_triangles_ = gpu_tri;
if (glMultiDrawElementsIndirectCount_) {
uint32_t compacted_sub_draws = 0;
uint32_t counts[2];
for (auto& [mid2, mm2] : models_gpu_) {
if (mm2.hidden || !mm2.gpu_draw_count_buffer) continue;
gl_->glGetNamedBufferSubData(mm2.gpu_draw_count_buffer, 0,
sizeof(counts), counts);
compacted_sub_draws += counts[0] + counts[1];
}
indirect_sub_draws_ = compacted_sub_draws;
}
}
FrameStats stats;
src/ifcviewer/ViewportWindow.h
-9
View File
@@ -126,14 +126,6 @@ struct ModelGpuData {
uint32_t gpu_mesh_command_count = 0;
uint32_t gpu_forward_command_count = 0;
// MDI compaction: non-empty commands are packed here by the pack shader.
// Same capacity as gpu_indirect_buffer; fwd at [0..2M), rev at [2M..4M).
// gpu_draw_count_buffer holds 2 × uint32: [fwd_count, rev_count], read
// by glMultiDrawElementsIndirectCount as GL_PARAMETER_BUFFER.
GLuint gpu_compacted_buffer = 0;
size_t gpu_compacted_capacity = 0;
GLuint gpu_draw_count_buffer = 0;
// Dynamic visible-instance index buffer (std430, binding = 1).
// Re-uploaded each frame from visible_flat_.
GLuint visible_ssbo = 0;
@@ -311,7 +303,6 @@ private:
// Phase 2: same + HiZ test → final survivors for color pass
GLuint cull_reset_program_ = 0;
GLuint cull_compact_program_ = 0;
GLuint cull_pack_program_ = 0;
// Depth-only program for the HiZ depth pre-pass — same vertex shader
// as main_program_, trivial fragment shader.