From 87d7b619bfb54ec0f95daeea96cc86e8c1b0e416 Mon Sep 17 00:00:00 2001
From: Mathias Paulin <mathias.paulin@irit.fr>
Date: Thu, 16 Dec 2021 15:16:02 +0100
Subject: [PATCH] temporary fix (because it's an hack) of issue #837

---
 Shaders/Picking/PickingPoints.geom.glsl | 62 +++++++++++++++++++++----
 src/Engine/Rendering/Renderer.cpp       | 12 ++++-
 2 files changed, 63 insertions(+), 11 deletions(-)

diff --git a/Shaders/Picking/PickingPoints.geom.glsl b/Shaders/Picking/PickingPoints.geom.glsl
index f1aede72765..ba2081ffe36 100644
--- a/Shaders/Picking/PickingPoints.geom.glsl
+++ b/Shaders/Picking/PickingPoints.geom.glsl
@@ -1,8 +1,5 @@
 #include "TransformStructs.glsl"
 
-layout( points ) in;
-layout( points, max_vertices = 1 ) out;
-
 in gl_PerVertex {
     vec4 gl_Position;
     float gl_PointSize;
@@ -16,11 +13,16 @@ out gl_PerVertex {
     float gl_ClipDistance[];
 };
 
+layout( points ) in;
+layout( triangle_strip, max_vertices = 4 ) out;
+
 layout( location = 0 ) in vec3 in_position[];
 layout( location = 1 ) in vec3 in_normal[];
 layout( location = 2 ) in vec3 in_eye[];
 
 uniform Transform transform;
+// 0.01 : default value, but will be set when rendering point cloud for picking
+uniform float pointCloudSplatRadius = 0.01;
 
 layout( location = 0 ) out vec3 out_position;
 layout( location = 1 ) out vec3 out_normal;
@@ -29,12 +31,52 @@ layout( location = 3 ) flat out int out_eltID;
 layout( location = 4 ) out vec3 out_eltCoords;
 
 void main() {
-    gl_Position   = transform.proj * transform.view * vec4( in_position[0], 1 );
-    out_position  = in_position[0];
-    out_normal    = in_normal[0];
-    out_eye       = in_eye[0];
-    out_eltID     = gl_PrimitiveIDIn;
-    out_eltCoords = vec3( 1, 0, 0 );
-    EmitVertex();
+    vec3 eye = -transform.view[3].xyz * mat3( transform.view );
+
+    // if no normal is provided, splats are aligned with the screen plane
+    vec3 normal = in_normal[0];
+    if ( length( normal ) < 0.1 ) { normal = normalize( eye - in_position[0] ); }
+
+    // orthonormal basis {u, v, normal}
+    vec3 u = vec3( 1, 0, 0 );
+    if ( abs( normal.x ) > 1e-3 ) { u = normalize( vec3( -normal.z / normal.x, 0, 1 ) ); }
+    vec3 v = normalize( cross( normal, u ) );
+
+    // (-1,+1)      (0,+1)     (+1,+1)
+    //        +-------+-------+
+    //        |1      |      3|
+    //        |       |       |
+    //        |       |       |
+    // (-1,0) +-------+-------+ (+1,0)
+    //        |       |       |
+    //        |       |       |
+    //        |0      |      2|
+    //        +-------+-------+
+    // (-1,-1)      (0,-1)     (+1,-1)
+
+    // quad corners
+    vec3 point[4];
+    point[0] = in_position[0] - pointCloudSplatRadius * ( u + v );
+    point[1] = point[0] + pointCloudSplatRadius * u * 2;
+    point[2] = point[0] + pointCloudSplatRadius * v * 2;
+    point[3] = point[0] + pointCloudSplatRadius * ( u + v ) * 2;
+
+    // uv coordinates
+    vec2 uv[4];
+    uv[0] = vec2( -1, -1 );
+    uv[1] = vec2( -1, +1 );
+    uv[2] = vec2( +1, -1 );
+    uv[3] = vec2( +1, +1 );
+
+    for ( int idx = 0; idx < 4; ++idx )
+    {
+        gl_Position   = transform.proj * transform.view * vec4( point[idx], 1 );
+        out_position  = point[idx];
+        out_normal    = normal;
+        out_eye       = in_eye[0];
+        out_eltID     = gl_PrimitiveIDIn;
+        out_eltCoords = vec3( 1, 0, 0 );
+        EmitVertex();
+    }
     EndPrimitive();
 }
diff --git a/src/Engine/Rendering/Renderer.cpp b/src/Engine/Rendering/Renderer.cpp
index 6d789f9c972..8639671e16e 100644
--- a/src/Engine/Rendering/Renderer.cpp
+++ b/src/Engine/Rendering/Renderer.cpp
@@ -17,6 +17,10 @@
 #include <Engine/Rendering/RenderObjectManager.hpp>
 #include <Engine/Scene/LightManager.hpp>
 
+// temporary fix for issue #837
+#include <Engine/Scene/GeometryComponent.hpp>
+
+
 #include <globjects/Framebuffer.h>
 
 #include <globjects/Texture.h>
@@ -473,7 +477,13 @@ void Renderer::renderForPicking(
                 Core::Matrix4 N = M.inverse().transpose();
                 pickingShaders[i]->setUniform( "transform.model", M );
                 pickingShaders[i]->setUniform( "transform.worldNormal", N );
-
+                // hack to pick point cloud (issue ##837)
+                auto pointCloud = dynamic_cast<Scene::PointCloudComponent*>( ro->getComponent() );
+                if ( pointCloud )
+                {
+                    pickingShaders[i]->setUniform( "pointCloudSplatRadius",
+                                                   pointCloud->getSplatSize() / 2.f );
+                }
                 // render
                 ro->getMesh()->render( pickingShaders[i] );
             }