I am an idiot: the quadtree code is now fixed.

tl;dr: needed more * by 2.

iab;wtd*: The index buffers on the GPU contain _two_ elements per object,
one for the top left of the object's bounding box, one for the bottom-right.
We were taking that into account when computing the number of indices to give
the DrawElements() call, but not when calculating the offset into the buffer.

Oops.

*: I am bored; want tedious detail

diff --git a/src/objectrenderer.cpp b/src/objectrenderer.cpp
index 998b62f..76aba52 100644 (file)
--- a/src/objectrenderer.cpp
+++ b/src/objectrenderer.cpp
@@ -42,7 +42,7 @@ void ObjectRenderer::RenderUsingGPU(unsigned first_obj_id, unsigned last_obj_id)
 
        m_shader_program.Use();
        m_ibo.Bind();
-       glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(first_index*sizeof(uint32_t)));
+       glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(2*first_index*sizeof(uint32_t)));
 }
 
 
@@ -328,7 +328,7 @@ void BezierRenderer::RenderUsingGPU(unsigned first_obj_id, unsigned last_obj_id)
        glUniform1i(m_shader_program.GetUniformLocation("bezier_buffer_texture"), 0);
        glUniform1i(m_shader_program.GetUniformLocation("bezier_id_buffer_texture"), 1);
        m_ibo.Bind();
-       glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(first_index*sizeof(uint32_t)));
+       glDrawElements(GL_LINES, (last_index-first_index)*2, GL_UNSIGNED_INT, (GLvoid*)(2*first_index*sizeof(uint32_t)));
 }
 
 /**