From 5ae098daff2097ffe3514a1ed06c8b007c4b02c8 Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Mon, 3 Oct 2022 01:02:05 -0500
Subject: [PATCH] Geo line requires two projection matrices

---
 scwx-qt/gl/geo_line.vert                    |  6 ++++--
 scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp | 13 +++++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/scwx-qt/gl/geo_line.vert b/scwx-qt/gl/geo_line.vert
index e232df95..4fea6910 100644
--- a/scwx-qt/gl/geo_line.vert
+++ b/scwx-qt/gl/geo_line.vert
@@ -12,6 +12,7 @@ layout (location = 2) in vec2 aTexCoord;
 layout (location = 3) in vec4 aModulate;
 
 uniform mat4 uMVPMatrix;
+uniform mat4 uMapMatrix;
 uniform vec2 uMapScreenCoord;
 
 flat out vec2 texCoord;
@@ -32,8 +33,9 @@ void main()
    texCoord = aTexCoord;
    modulate = aModulate;
 
-   vec2 p = latLngToScreenCoordinate(aLatLong) + aXYOffset - uMapScreenCoord;
+   vec2 p = latLngToScreenCoordinate(aLatLong) - uMapScreenCoord;
 
    // Transform the position to screen coordinates
-   gl_Position = uMVPMatrix * vec4(p, 0.0f, 1.0f);
+   gl_Position = uMapMatrix * vec4(p, 0.0f, 1.0f) -
+                 uMVPMatrix * vec4(aXYOffset, 0.0f, 0.0f);
 }
diff --git a/scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp b/scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp
index 2ab6047f..56f8c16b 100644
--- a/scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp
+++ b/scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp
@@ -36,6 +36,7 @@ public:
        modulateColor_ {std::nullopt},
        shaderProgram_ {nullptr},
        uMVPMatrixLocation_(GL_INVALID_INDEX),
+       uMapMatrixLocation_(GL_INVALID_INDEX),
        uMapScreenCoordLocation_(GL_INVALID_INDEX),
        vao_ {GL_INVALID_INDEX},
        vbo_ {GL_INVALID_INDEX}
@@ -58,6 +59,7 @@ public:
 
    std::shared_ptr<ShaderProgram> shaderProgram_;
    GLint                          uMVPMatrixLocation_;
+   GLint                          uMapMatrixLocation_;
    GLint                          uMapScreenCoordLocation_;
 
    GLuint vao_;
@@ -66,7 +68,6 @@ public:
    void Update();
 };
 
-// TODO: OpenGL context with shaders
 GeoLine::GeoLine(std::shared_ptr<GlContext> context) :
     DrawItem(context->gl()), p(std::make_unique<Impl>(context))
 {
@@ -90,6 +91,13 @@ void GeoLine::Initialize()
       logger_->warn("Could not find uMVPMatrix");
    }
 
+   p->uMapMatrixLocation_ =
+      gl.glGetUniformLocation(p->shaderProgram_->id(), "uMapMatrix");
+   if (p->uMapMatrixLocation_ == -1)
+   {
+      logger_->warn("Could not find uMapMatrix");
+   }
+
    p->uMapScreenCoordLocation_ =
       gl.glGetUniformLocation(p->shaderProgram_->id(), "uMapScreenCoord");
    if (p->uMapScreenCoordLocation_ == -1)
@@ -155,8 +163,9 @@ void GeoLine::Render(const QMapbox::CustomLayerRenderParameters& params)
 
       p->Update();
       p->shaderProgram_->Use();
+      UseDefaultProjection(params, p->uMVPMatrixLocation_);
       UseMapProjection(
-         params, p->uMVPMatrixLocation_, p->uMapScreenCoordLocation_);
+         params, p->uMapMatrixLocation_, p->uMapScreenCoordLocation_);
 
       // Draw line
       gl.glDrawArrays(GL_TRIANGLES, 0, 6);