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ifcviewer: add section-plane clipping plumbing

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Adds a clip-plane pipeline used by the upcoming section tool:

- Up to 8 SectionPlane{n, d} entries, AND-combined as
  fragment-shader discard against world position.  Main and pick
  fragment shaders both honour the planes, so cut areas are
  neither drawn nor selectable.
- Main vertex shader now passes v_world_pos through.
- Pick FBO grows two attachments (RGB32F world position, RGB16F
  world normal) and the pick shader writes both alongside the
  object id.  pickSurfaceAt() does a single readback of all
  three.  Existing pickObjectAt() still works unchanged for
  callers that just want the id.
- addSectionPlaneAtSurface(point, normal) auto-flips the normal
  toward the camera so the first click immediately cuts the
  camera-facing half.

No UI yet — that's the next commit (gizmo, drag, K shortcut).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Dion Moult
2026-04-30 12:13:17 +10:00
parent a06e5ecdf5
commit 309e20009c
2 changed files with 201 additions and 9 deletions
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src/ifcviewer/ViewportWindow.cpp
+163 -8
View File
@@ -94,6 +94,7 @@ uniform uint u_selected_id;
out vec3 v_normal;
out vec4 v_color;
out vec3 v_world_pos;
flat out uint v_object_id;
flat out uint v_selected;
@@ -115,6 +116,7 @@ void main() {
vec3 pos_local = mix(mq.aabb_min.xyz, mq.aabb_max.xyz, a_position_q);
vec4 world = inst.transform * vec4(pos_local, 1.0);
v_world_pos = world.xyz;
gl_Position = u_view_projection * world;
// Rotate the normal by the upper-3x3 of the transform. BIM placements
@@ -149,14 +151,25 @@ static const char* MAIN_FRAGMENT_SHADER = R"(
#version 450 core
in vec3 v_normal;
in vec4 v_color;
in vec3 v_world_pos;
flat in uint v_object_id;
flat in uint v_selected;
uniform vec3 u_light_dir;
// Section planes — clip the half-space dot(n,p)+d > 0. AND-combined.
const int MAX_CLIP_PLANES = 8;
uniform int u_clip_count;
uniform vec4 u_clip_planes[MAX_CLIP_PLANES];
out vec4 frag_color;
void main() {
for (int i = 0; i < u_clip_count; ++i) {
if (dot(u_clip_planes[i].xyz, v_world_pos) + u_clip_planes[i].w > 0.0) {
discard;
}
}
// v_normal already has the reflection flip applied in the vertex
// shader. When backface culling is off, open shells let us see the
// "wrong" side of a face — flip based on gl_FrontFacing so both
@@ -177,6 +190,7 @@ static const char* PICK_VERTEX_SHADER = R"(
#version 450 core
#extension GL_ARB_shader_draw_parameters : require
layout(location = 0) in vec3 a_position_q;
layout(location = 1) in vec2 a_normal_oct;
struct InstanceRecord {
mat4 transform;
@@ -199,6 +213,15 @@ layout(std430, binding = 2) readonly buffer Meshes {
uniform mat4 u_view_projection;
flat out uint v_object_id;
out vec3 v_world_pos;
out vec3 v_world_normal;
vec3 octDecode(vec2 e) {
vec3 n = vec3(e.xy, 1.0 - abs(e.x) - abs(e.y));
if (n.z < 0.0) n.xy = (1.0 - abs(n.yx)) * vec2(n.x >= 0.0 ? 1.0 : -1.0,
n.y >= 0.0 ? 1.0 : -1.0);
return normalize(n);
}
void main() {
uint slot = uint(gl_BaseInstanceARB) + uint(gl_InstanceID);
@@ -206,7 +229,16 @@ void main() {
InstanceRecord inst = instances[iid];
MeshQuant mq = meshes[inst.mesh_id];
vec3 pos_local = mix(mq.aabb_min.xyz, mq.aabb_max.xyz, a_position_q);
gl_Position = u_view_projection * inst.transform * vec4(pos_local, 1.0);
vec4 world = inst.transform * vec4(pos_local, 1.0);
v_world_pos = world.xyz;
gl_Position = u_view_projection * world;
vec3 n_local = octDecode(a_normal_oct);
mat3 rot = mat3(inst.transform);
vec3 n = rot * n_local;
if (determinant(rot) < 0.0) n = -n;
v_world_normal = normalize(n);
v_object_id = inst.object_id;
}
)";
@@ -214,8 +246,27 @@ void main() {
static const char* PICK_FRAGMENT_SHADER = R"(
#version 450 core
flat in uint v_object_id;
out uint frag_id;
void main() { frag_id = v_object_id; }
in vec3 v_world_pos;
in vec3 v_world_normal;
const int MAX_CLIP_PLANES = 8;
uniform int u_clip_count;
uniform vec4 u_clip_planes[MAX_CLIP_PLANES];
layout(location = 0) out uint frag_id;
layout(location = 1) out vec3 frag_pos;
layout(location = 2) out vec3 frag_normal;
void main() {
for (int i = 0; i < u_clip_count; ++i) {
if (dot(u_clip_planes[i].xyz, v_world_pos) + u_clip_planes[i].w > 0.0) {
discard;
}
}
frag_id = v_object_id;
frag_pos = v_world_pos;
frag_normal = normalize(v_world_normal);
}
)";
static const char* AXIS_VERTEX_SHADER = R"(
@@ -471,7 +522,9 @@ ViewportWindow::~ViewportWindow() {
if (axis_program_) gl_->glDeleteProgram(axis_program_);
if (pivot_program_) gl_->glDeleteProgram(pivot_program_);
if (pick_fbo_) gl_->glDeleteFramebuffers(1, &pick_fbo_);
if (pick_color_tex_) gl_->glDeleteTextures(1, &pick_color_tex_);
if (pick_color_tex_) gl_->glDeleteTextures(1, &pick_color_tex_);
if (pick_pos_tex_) gl_->glDeleteTextures(1, &pick_pos_tex_);
if (pick_normal_tex_) gl_->glDeleteTextures(1, &pick_normal_tex_);
if (pick_depth_rbo_) gl_->glDeleteRenderbuffers(1, &pick_depth_rbo_);
if (hiz_fbo_) gl_->glDeleteFramebuffers(1, &hiz_fbo_);
if (hiz_depth_tex_) gl_->glDeleteTextures(1, &hiz_depth_tex_);
@@ -1745,15 +1798,27 @@ uint32_t ViewportWindow::pickObjectAt(int x, int y) {
int h = height() * devicePixelRatio();
if (pick_width_ != w || pick_height_ != h) {
if (pick_fbo_) gl_->glDeleteFramebuffers(1, &pick_fbo_);
if (pick_color_tex_) gl_->glDeleteTextures(1, &pick_color_tex_);
if (pick_depth_rbo_) gl_->glDeleteRenderbuffers(1, &pick_depth_rbo_);
if (pick_color_tex_) gl_->glDeleteTextures(1, &pick_color_tex_);
if (pick_pos_tex_) gl_->glDeleteTextures(1, &pick_pos_tex_);
if (pick_normal_tex_) gl_->glDeleteTextures(1, &pick_normal_tex_);
if (pick_depth_rbo_) gl_->glDeleteRenderbuffers(1, &pick_depth_rbo_);
gl_->glCreateFramebuffers(1, &pick_fbo_);
gl_->glCreateTextures(GL_TEXTURE_2D, 1, &pick_color_tex_);
gl_->glTextureStorage2D(pick_color_tex_, 1, GL_R32UI, w, h);
gl_->glNamedFramebufferTexture(pick_fbo_, GL_COLOR_ATTACHMENT0, pick_color_tex_, 0);
gl_->glCreateTextures(GL_TEXTURE_2D, 1, &pick_pos_tex_);
gl_->glTextureStorage2D(pick_pos_tex_, 1, GL_RGB32F, w, h);
gl_->glNamedFramebufferTexture(pick_fbo_, GL_COLOR_ATTACHMENT1, pick_pos_tex_, 0);
gl_->glCreateTextures(GL_TEXTURE_2D, 1, &pick_normal_tex_);
gl_->glTextureStorage2D(pick_normal_tex_, 1, GL_RGB16F, w, h);
gl_->glNamedFramebufferTexture(pick_fbo_, GL_COLOR_ATTACHMENT2, pick_normal_tex_, 0);
gl_->glCreateRenderbuffers(1, &pick_depth_rbo_);
gl_->glNamedRenderbufferStorage(pick_depth_rbo_, GL_DEPTH_COMPONENT24, w, h);
gl_->glNamedFramebufferRenderbuffer(pick_fbo_, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, pick_depth_rbo_);
static const GLenum draw_bufs[3] = {
GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2
};
gl_->glNamedFramebufferDrawBuffers(pick_fbo_, 3, draw_bufs);
pick_width_ = w;
pick_height_ = h;
}
@@ -1775,6 +1840,91 @@ uint32_t ViewportWindow::pickObjectAt(int x, int y) {
return pixel;
}
bool ViewportWindow::pickSurfaceAt(int x, int y,
uint32_t& object_id_out,
QVector3D& world_pos_out,
QVector3D& world_normal_out) {
const uint32_t id = pickObjectAt(x, y);
if (id == 0) return false;
const int px = x * devicePixelRatio();
const int py = (height() - y) * devicePixelRatio();
float pos[3] = {0, 0, 0};
float normal[3] = {0, 0, 0};
gl_->glGetTextureSubImage(pick_pos_tex_, 0, px, py, 0, 1, 1, 1,
GL_RGB, GL_FLOAT, sizeof(pos), pos);
gl_->glGetTextureSubImage(pick_normal_tex_, 0, px, py, 0, 1, 1, 1,
GL_RGB, GL_FLOAT, sizeof(normal), normal);
QVector3D n(normal[0], normal[1], normal[2]);
if (n.lengthSquared() < 1e-8f) {
// Pick succeeded for object_id but normal attachment was empty —
// unexpected (shader writes it on every covered fragment), so bail
// rather than hand the caller a degenerate plane.
return false;
}
object_id_out = id;
world_pos_out = QVector3D(pos[0], pos[1], pos[2]);
world_normal_out = n.normalized();
return true;
}
void ViewportWindow::uploadClipPlaneUniforms(GLuint program) {
const GLint u_count = gl_->glGetUniformLocation(program, "u_clip_count");
if (u_count < 0) return; // program does not declare clipping uniforms
const int n = qMin(int(section_planes_.size()), MaxSectionPlanes);
gl_->glUniform1i(u_count, n);
if (n == 0) return;
float packed[MaxSectionPlanes * 4] = {};
for (int i = 0; i < n; ++i) {
packed[i * 4 + 0] = section_planes_[i].n.x();
packed[i * 4 + 1] = section_planes_[i].n.y();
packed[i * 4 + 2] = section_planes_[i].n.z();
packed[i * 4 + 3] = section_planes_[i].d;
}
const GLint u_planes = gl_->glGetUniformLocation(program, "u_clip_planes");
if (u_planes >= 0) {
gl_->glUniform4fv(u_planes, n, packed);
}
}
bool ViewportWindow::addSectionPlaneAtSurface(const QVector3D& point,
const QVector3D& normal) {
if (int(section_planes_.size()) >= MaxSectionPlanes) {
qWarning("Section plane cap (%d) reached", MaxSectionPlanes);
return false;
}
QVector3D n = normal;
if (n.lengthSquared() < 1e-8f) return false;
n.normalize();
// Auto-flip so the plane clips the camera-facing half — first click
// immediately cuts away what's between the user and the clicked surface.
const QVector3D eye_dir = (camera_eye_ - point);
if (QVector3D::dotProduct(n, eye_dir) < 0.0f) n = -n;
SectionPlane p;
p.n = n;
p.d = -QVector3D::dotProduct(n, point);
section_planes_.push_back(p);
have_cached_cull_ = false;
requestUpdate();
return true;
}
void ViewportWindow::removeSectionPlane(int index) {
if (index < 0 || index >= int(section_planes_.size())) return;
section_planes_.erase(section_planes_.begin() + index);
have_cached_cull_ = false;
requestUpdate();
}
void ViewportWindow::clearSectionPlanes() {
if (section_planes_.empty()) return;
section_planes_.clear();
have_cached_cull_ = false;
requestUpdate();
}
void ViewportWindow::cullAndUploadVisible(ModelGpuData& m, const float planes[6][4],
float focal_px, float min_pixel_radius) {
cullModelCpu(m, planes, focal_px, min_pixel_radius);
@@ -2112,6 +2262,7 @@ void ViewportWindow::render() {
gl_->glUniformMatrix4fv(u_vp, 1, GL_FALSE, vp.constData());
gl_->glUniform3f(u_light, 0.3f, 0.5f, 0.8f);
gl_->glUniform1ui(u_sel, selected_object_id_);
uploadClipPlaneUniforms(main_program_);
visible_triangles_ = 0;
visible_objects_ = 0;
@@ -2550,8 +2701,11 @@ void ViewportWindow::render() {
void ViewportWindow::renderPickPass() {
gl_->glBindFramebuffer(GL_FRAMEBUFFER, pick_fbo_);
gl_->glViewport(0, 0, pick_width_, pick_height_);
GLuint clear_val = 0;
gl_->glClearBufferuiv(GL_COLOR, 0, &clear_val);
const GLuint zero_id = 0;
const float zero3[4] = {0, 0, 0, 0};
gl_->glClearBufferuiv(GL_COLOR, 0, &zero_id);
gl_->glClearBufferfv (GL_COLOR, 1, zero3);
gl_->glClearBufferfv (GL_COLOR, 2, zero3);
gl_->glClear(GL_DEPTH_BUFFER_BIT);
QMatrix4x4 vp = proj_matrix_ * view_matrix_;
@@ -2561,6 +2715,7 @@ void ViewportWindow::renderPickPass() {
gl_->glUseProgram(pick_program_);
GLint u_vp = gl_->glGetUniformLocation(pick_program_, "u_view_projection");
gl_->glUniformMatrix4fv(u_vp, 1, GL_FALSE, vp.constData());
uploadClipPlaneUniforms(pick_program_);
gl_->glFrontFace(GL_CCW);